The past two times we drove, we went through Dothan and onto I-10 once and Atlanta (via I-75) the other time. They both took about 9.5 hours each way. Both trips were made during the day; leaving at 8-9am from the starting point. The one thing I don’t like about going through South Alabama is the stop and go due to traffic lights once you pass Montgomery. They’re further apart out of the cities (Dothan, mainly) but when you go through them it’s kind of a mess.
On the flipside, I don’t really like I-20/I-75 simply because of Atlanta traffic (and their policing). Though I’m not a speeder, I have to keep an eye out for ‘the man’ when I’m entering Atlanta metro and the outskirts. Not that I should complain about this, but I think we all probably go a bit over the speed limit.
My wife works in Healthcare and I’m an engineer so we understand being exhausted from ‘all those years of school’, but hey, it’s Disney World. You’re gonna get pumped when you get there. It’s just a matter of how long the adrenaline will last.
If you guys can switch up drivers then I think you’ll be alright. It really comes down to me feeling like I got my money’s worth. If I hit a park at 9am and feel beat by 4pm with 6 hours left on my ticket then I feel like I did myself (and my wallet) a disservice. And you mentioned being very money conscious, so I was throwing that bit out there.
Do you work nightshifts? My wife does. She works 12 hours shifts at the hospital. If we wanted to drive all night she could do it while I slept the whole way. I wouldn’t put that on her, but it’s possible. If you work night shift then you guys are set.
I’m not a morning person by any means, so to be quite honest, I’d prefer to head out mid-afternoon and drive 10 hours straight to be there by 12-1 am. I usually catch a second wind around 10pm on the weekends anyway, so this would fit. The problem is that as soon as I get to the resort I’d fall apart and I wouldn’t be able to wake up early the next morning to make it a full day. That’s why we don’t do that.
It’s simply worked well for us to drive during the day, arrive at night, shop around a couple hours, eat and then go to bed. Then we’re on our normal schedule (don’t forget that you lose an hour) and ready to rock the next day.
As for your fiancé saying he’ll do whatever you want, … that’s just us guys. We just kind of go with the flow.
So, a few cons of driving all night are:
1) You’re going to be tired the next day at some point
2) You may feel you’ve ‘wasted’ a day if you don’t stay all day at the park and get your money's worth
3) Having to drive at night when your body is telling you “hey, it’s time to go to sleep” and putting yourself at risk if the driver is physically tired and cannot drive (driving 10+ hours can be exhausting)
Pros:
1) Save money on getting an extra night at (any) hotel
2) If timed right, you can make it to the parks at opening with everyone else at the resort(s)
3) Less Traffic and easier drive
It seems to me that it simply comes down to money/time value. Is it worth an extra (say) $80-100 hotel night to get a good night’s rest at the beginning of your trip? Do you think you’ll be able to be okay with calling it a night early your first night and catching up on sleep so you don’t wreck the rest of your trip? If so, then drive overnight and get there at 6am.
BUT we'd be better rested then driving in all night then parks all day! 
(3) I'd hate to leave my pups longer than we'd have to ... but what's one more day after leaving them for 7 already! 
why didn't I think of disney tunes!!!! thanks!)
