I have been following this thread for a while, as we were back and forth on the stroller issue for our trip in Sept. My daughter had just turned 6, and we really worried about her ability to keep up in the heat and humidity that time of year. We ended up opting not to take the stroller. We were stunned on how she ran us Disney vets into the ground. We did multiple days over 8 miles, and she was constantly pushing us to keep going. She has an average activity level in daily life, no sports etc., but had zero issues walking with regular stops for rest in the parks. Hope that helps.
Jennie