Do what you think will work for your family. My kids are 5 1/2 and 8. We no longer need stroller for regular outings, but I will continue to use a stroller at Disney World. Disney World is a ton of walking and I bring a lot of stuff into the parks with us, so I want it to carry our stuff as much as for our kids to ride in (and, not gonna lie, I have perched on the edge of the stroller to rest when the kids were running around while we were waiting for fireworks and I was tired of standing, lol) As far as the kids go, our kids could make it through the day at Disney without the stroller if they had to, but I would hate to not have it at night when leaving the parks-we go rope drop to close, and they can handle it fine until it is time to leave, at which point they are exhausted and it would not be pretty trying to leave without the stroller. If someone were willing to push me and I could fit, I would gladly climb in a stroller myself at that point!
Honestly I will probably bring one even when the kids are way, way too big, because I use it as a rolling locker for our non-valuables such as rain ponchos, water bottles, snacks, sunscreen, princess dresses for the girls to wear during meet and greets, etc. No way am I walking all the way to wherever the lockers are every time I want to grab a snack or something, and we don't buy all our snacks/meals in the park because it gets expensive. I'm not good at traveling light at Disney, and I'd prefer pushing and parking a stroller over carrying all of our stuff with me all day.