Beer 001 - Very fast priming?

I had a quick look at the PET bottles that I filled with Beer 001 yesterday, perhaps I should have given it a stir to agitate the yeast and see if it would ferment a little more. The bottles, although not rock solid, have already lost their squished parts, so the priming seems to be happening awfully fast. Of course I'm not sure if that is normal or not. Oh well, I'll leave them to get rock hard and then move them to the cellar. My readings of the forum seem to indicate that I should be alright with PET bottles and the maximum pressure they can take.