No one can say someone is 'too old' for a stroller, that decision is yours to make. There are so many variables at play that its impossible for anyone here to say what will or will not work. There is a contingent of people within these boards that believe as soon as a child is able to walk they ought to frog march with 55lbs of backpack and fluid lol... apparently its a sign of good parenting and a right of passage?!? lol
OK, well maybe that's exaggerating a little! A stroller is a tool, it is a tool to help a situation. This 'help' could come in many forms but only you know what it is it will help with. If the stroller will help make your life a little easier and be beneficial to you then rent one or take one and use it. If you feel you can go without then go without. I wouldn't worry what other people would say or perceive from your 8yr old being in a stroller. My wife would get in it if I could push it! haha
For some its a burden, for others its a godsend. Just decide what your priorities are and what is good for you and see where it fits.