Merlin loves his tummy rubbed and will stretch out and do all kinds of weird contortions to be stroked in just the "right" place. However when he's had enough, the four paws will come up and he will gently bite my wrist as if to say "enough is enough", before giving it a quick lick and flipping over. A quick swipe with the paw (claws in) is also a sign that he's had enough tummy rubbing.
However if you tried to do this to Freya, she'd be walking away with half of your arm in her mouth !
I think some cats have a stroking tolerance ranging from wrist-numbingly long to "touch me again and I'll kill you". I suppose it depends on the cat and how much socialisation / handling they had from when they are tiny.
Our two were both feral rescue-cats and had the same upbringing until we adopted them, but both have completely opposite personalities. One loves to be stroked for hours, the other "just" tolerates it (but is getting better with each week that goes by)