When is to old for stroller?

Ok so my daughter will be 4 when this one is born. And yes i know thats pushing it to ride in the stroller. But im tempted to get one of those sit and stand.. anyone have one? i mean the weight limits are like 50 lbs for each seat/child. My daughter is only 27!

I understand it may seem lazy and my daugheter walks most places. I rarley use the stroller anymore. But my reasoning would be for times when i still do such as a trip to zoo or shopping at the mall.. places we would be walking alot. Or i would need to concentrate on shopping.

Also just feel its safer expecially in busy places... im somewhat a scatter brained person, get overwhelmed easily and it seems it would help me keep up with 2 kids!

What do yall think? Would i be waisting my money to get a sit and stand...would she outgrow it in 6 months. whats the oldest age u would have in a sit and stand?