My question is, is it possible to properly train for Dopey without running 20+ miles in one go? I think realistically, the longest run I’d be able to do would be ~2hrs, and even that would be a stretch.
First, realize that you don't need a Dopey specific training plan. If you choose a good marathon training plan, then you will be properly prepared. The key is choosing a training plan that you feel at the outset you can commit to 100%. If you know you can't do 90 min of running on Wednesdays, don't choose a training plan that has 90 min on Wednesdays. Don't go into the training plan from the outset making major changes. Instead, find a training plan that makes it so it revolves around your life instead of your life revolving around the running.
Second, I'm a big believer in the concept of training by time instead of miles. I've seen the methodology be successful for runners aiming for sub-3, and for runners aiming for sub-7. In fact, when evaluated by time instead of mileage, the plans for a sub-3 and a sub-7 aren't necessarily all that different than each other. Yes, the sub-3 runner may do 19 miles max and the sub-7 runner does 10 miles max, but if we evaluate it by how long you're running for and the effort level you're giving the bodies of these two runners are going to perceive the activity similarly. It's the basis of the theory of training load (duration and effort matter more than mileage because mileage is simply a function of the other two).
Thirdly, typically I place a maximum limit of 150-180 min for the longest run at long run pace (for continuous runners that's about 9% slower than M Tempo and for run/walkers that's 2 minutes slower than M Tempo). If someone wanted to do an even longer run, then the first consideration is to dramatically slow the long run pace. But you're looking for the opposite. You want a maximal long run at 2 hours. So the question back would be, why? What leads you to believe that you can't successfully train beyond 2 hours? Is it a time limit (like I've got so many other life commitments that the most I can commit to on a single weekend day occurring 2-3 times in Nov/Dec is 2 hours)? Or is it from a perspective of, every time I've trained for a race prior, I've had issues going beyond 2 hours? Because if it's the latter, then it may be an issue that your previous training was improper and that's why you couldn't successfully train beyond 2 hours. If the pace was perhaps too quick or the other training in the week was too light, would be the first two things I'd look at in previous training to help solve the potential issue. It's common for most runners, but especially those who which are slower, to think that they have to train fast on their long runs in order to be successful on race day. That's a fallacy. Quite the opposite actually. You have to go pretty slow for the training to be unproductive, but it's really easy to go too fast. For instance, someone who runs a 3hr HM (13:44) or 6:15 M (14:19) should be doing their long runs at 15:36 to 16:19. But I guarantee you most 3 hr HM runners don't go slow enough in training. So they feel as if those long runs are too much for them to handle.
But let's say you're the opposite. That it isn't the physical toll of the long run, but rather the time availability is the main issue when limiting to 2 hours on your max weekend long run. That would be a short long run, but it's not impossible. It'll then come down to a commitment during the rest of the week. I've written hundreds of successful training plans in the past six years. To my recollection, I've written one where someone completed a marathon on a 2 hr long run. I would want to see that runner get in at least six hours of training in the peak week. So if you're doing 2 hrs max on Sunday, then you'd need to get 4 hours of running from the other six days minimally. Something like:
M- OFF
T- 45 min
W- 90 min
R- 45 min
F- OFF
Sa- 90 min
Su- 120 min
Could be successful. That's 6.5 hrs. The key is realizing that different durations will effect the body differently. The golden zone of endurance training is that 60-90 min training run. Lots of benefits, and comparatively minimal recovery. Whereas training runs that take 120-150 min take a significant more time to recover from. So to bolster your overall training, we include multiple bouts of training in that 60-90 min area.
So to answer your other question, where can I find training plans that don't go up to 20 miles in a marathon training plan? If we stop and think for a second we can figure out a solution. Firstly, we discussed if how a training plan is written in terms of duration and effort, then whoever completes the plan should have a similar response. Whether they're a sub-3 or a sub-7. So that means, if we covert any training plan from a mileage based one to what a duration based scheme would look like for a 4:00hr marathon runner (many pre-written plans have 3:30-4:00 hr runners in mind), then we'll have a general idea as to how much duration we should be doing if we're a slower runner. Let's use the Hansons Beginner plan as an example.
These are the training paces for a 4:00hr runner.
Peak week of the Hansons Beginner plan is:
M- 7 miles at EA
T- 1 mile WU + 2 x 3 mile at M Tempo-10 sec w/ 0.25 mile RI + 1 mile CD
W- OFF
R-1 mile WU + 10 mile M Tempo + 1 mile WU
F- 6 miles at EA
Sa- 6 miles at EB
Su- 16 miles at LR
56 miles total
Using the paces above, we convert that to time
M- 77 min at EA
T- 11 min WU + 2 x 27 min at M Tempo-10 sec w/ 3 min RI + 11 min CD
W- OFF
R-11 min WU + 90 min M Tempo + 11 min WU
F- 60 min at EA
Sa- 60 min at EB
Su- 160 min at LR
9.2 hrs total.
So now the Hansons Beginner plan can be useable for anyone from a sub-3 to sub-7 runner if you just go through and convert mileage to time. One common misconception is that Hansons wants you to do 16 mile whether you're a sub-3 or a sub-7 runner. But if you read the book they talk about time limits for certain types of runs. So Hansons might suggest you do 20 miles, if you can do those 20 miles in 175min. Conversely, they Hansons book might recommend capping the LR at 12 miles if you hit their time threshold for that type of run. So even the plans written in the book need to be evaluated in terms of duration based on your paces.
I'd recommend trying to find a training plan that peaks in mileage from 6-9 hrs. Going lower than 6 hrs is iffy (but doable) for a marathon, and many recreational runners don't need to exceed 9 hrs at peak to reach near peak physical capability. Veterans go past 9 hrs, but that's because they're trying to squeeze the lemon. Hansons (Luke Humphrey) and Jack Daniels are two authors that come to mind when looking for training plans that limit the long run. Their books are very useful guides on proper marathon training for all levels.
Alternatively, you work with a coach that can create something more custom to you and your life. I'd venture to guess that if you end up deciding that 2 hours is a hard limit on your maximum training run, you're going to struggle to find pre-written plans even when converting them to time based plans. I know it's possible because I've done it once before, but it wouldn't be easy by any stretch.
Here's some light reading from some of my previous posts that are tangentially related to this conversation.
Eureka! The Quintessential Running Post
Train slow to race fast: Why running more slowly and capping the long run at 2.5 hours may dramatically improve your performance
Why should your average training pace be much much slower than your goal half marathon pace?
Why am I doing this run? The question every runner should be asking themselves.
Glycogen Supercompensation (AKA Carb Loading)
The Long Run Mindset: How to train at 16 miles but run a 26.2 mile race
The Marathon is 99% Aerobic (and 95% for HM and so on): So how to train for it!
Two kinds of impressive: The person who finishes first may not be the most impressive, it could be who finished last.
Advice for Newbies #1
Advice for Newbies #2
Advice for Newbies #3
Advice for Newbies #4
Advice for Newbies #5