Our twins are now 5 and we've been taking them to disney since they were babies, going to disney every 5-6 months, so we've hit every stage. Last trip was last month. They still needed our double jogger, big time. Not to sit in all day, of course, but by the end of the day they were tired out. Picture this: we got caught in the back of MK when Wishes started (big mistake...). Kids were exhausted, so we put them in the jogger and they watched Wishes and then immediately fell asleep. It took us about 45 minutes to get through the crowd and to the exit -- the kids slept the entire time in the jogger. So we parents could take our time and relax without worries of tired kids. Now I'm not saying this would be the case for your kids, but I just wanted to give an example of what happened to us last month.
As far as double versus single strollers, we prefer a double but we have twins and they do everything at the same time, so the double makes the most sense for us. I should also point out that we've mainly stayed at either monorail resorts or Epcot resorts, so the double stroller has rarely been an issue as far as folding it up, etc. I will admit it is somewhat of a pain for us on a bus, but not nearly as painful now that the kids are older versus when they were baby stages.