When Is Too Big for a Stroller?

In the past, I’ve admitted to my obsession with strollers. It’s one of the pieces of baby gear that I really enjoyed shopping for and using—for reasons of style, ease, practicality… But my older son is almost 4, and I’ve recently come to realize that (gulp!) he may be getting too old for a stroller. If we’re out with his younger brother (who’s approaching 2), he normally walks or rides on the skateboard-like roller board attached to our stroller, but there are times when we’re out for a full day of walking around NYC, and asking him to walk several miles seems, well, too much to ask of a kid who’s only 3—which is when we pull out the double stroller, to allow him a break if need be.
Plus: Stroller Buying Guide
 
Personally, I don’t think I’m infantilizing him or coddling him—I’m just being realistic about the limits of his energy and good behavior. And given the choice between allowing him to ride for a bit or, say, putting him on a kid leash to keep him close by when his listening skills seem to diminish with the miles walked, I’ll gladly permit him some rest. But, even though he’s well below the weight limit for our stroller, he does look kind of big in it (er, we have a mini double stroller, because what New Yorker has room for a full-size one?!)—which apparently may make me the target of fans of the blog Toobigforstroller. People can email photos of kids who look too big for their stroller (or grocery cart kid’s seat) to the blog, where they are published (often without blocking out the kids’ faces) along with some snarky (sometimes funny, sometimes kinda harsh) commentary. Ouch.
Plus: Truly Ridiculous Parenting Products

While some of the submissions do look ridiculous, there are plenty of good reasons these kids could be in strollers—everything from being at the end of an exhausting day at the zoo/out on the town/etc, to developmental disabilities. There’s just plain laziness on the parent’s or kid’s part too, I guess. What’s your take? Is there a point at which a kid just too old or too big for a stroller?