Do other people have similar experiences?
Regularly, I am not allowed to catch a pet when my Pet Journal says I own 498 pets - which, imho, leaves room for two more (and ithe pet I wanna catch isn't one I already own three samples of).
But I've also had a situation where I hadn't checked for a while, and then found I had 510 pets! (And this was not due to pre-pandaria pets, as I didn't have that much when I started catching)
I wish this was somehow predictable. I'd hate running into a real rare Rare and then not be allowed to catch it! (I understand the solution here is to make sure I always keep it under 496 or so, but I just don't wanna dispose of all my double pre-MoP pets.)
Anyway, I hope 5.1 will be implemented soon, as I am now able to catch pets in Pandaria, and there are sooo many I don't own yet!