I've had people thank me for being "thoughtful" and not making a little one walk for too long. I've also had stupid, unthoughtful people think it's ridiculous
I think it's savage to expect a little dog to walk as long and far as we can. My legs a huge (and I'm tiny) compare to my babies', I can cover in one stride what takes my babies 3-4 strides. So they tire easier and faster.
They have their entire backs exposed to the sun from above and the heat from the bottom (concrete shoots heat/cold right back up, so they get double exposure), I only have my head at full exposure.
Not only can they go in the stroller when tired, but also when they're scared by bigger dogs or fast walking crowds.
It's just safe for them any way I look at it