
God I'd have a fit if a bitch of mine strained for an hour to deliver a pup,
I get worried if they go longer than two hours between pups, but actually straining is normally seconds to half a minute.
So much is breed type/size dependant or even family lines.
I have had pups come so fast one after another the bitch was totally overwhelmed and needed to be stopped from trying to flea, and wouldn't settle and accept pups until 6th pup born.
I have also had a bitch have 4 hour gaps between 4 pups and then had 5 the stillborn following Oxytocin at vet, yet delivered her next litter of 7 much more quickly.