The dog would most likely have a heat stroke and go down. Hopefully it will never happen that your bulldog would have to stay caught that long but if it happens then yes I would expect a catchdog to stay caught as long as his body would allow..
I saw where someone had posted they like a catchdog with some self preservation, well if a catchdog that I'm feeding cares anything about "self preservation" then he better CATCH when I turn him loose..
But what a man feed is totally up to him..

X4
Coming off a hog from overheating and going under water are two things I will never fault a catch dog for. By overheating, I mean to the point where their body can't physically function anymore. I've been on that end of the deal many times, it's not fun. That's why I grit my teeth when I read about all these people that send their catch dogs in from a 1/2 mile out etc... and i've never seen a dog drown themselves.

There is a breaking point.