Never, never, and I mean ever pull, pick, or peal your callus's or blisters.
Yes, it will come back. Your finger may take on a "custom" shape, and it may take a very long time to become the normal shape again.
yes, it is normal to wear on your callus's.
I recently took a long time, about 6 months, off playing (not enough time to lose my callus's as they are very well established) and then I was practicing up for a band audition and I played so much I raised a 'hot spot' (didn't really blister up as the callus is so thick) .... it took weeks for the thing to appear, and then it hung around for weeks. It was over a month and a half from the time I felt the hot spot and knew that the damage was done, untill the calus/blister started to crack and let go. I resitsed the urge to pick or peel and healed just fine and there was no pain at any point, I played all through that month and a half woth no problem. IF I had given in to urges to pick at it, I would have exposed a sensitive pink area of fresh skin that wasn't ready to take on the world yet and I wouldn'y have been able to play that day.
If you just leave your fingers alone, and never pick at callus's, blisters, or shedding skin hang-y things they will always heal just fine on there own and you can keep playing bass everyday. Pick, and they heal sometimes with wierd shapes (flat spots, craters) and you'll cause pain that will prevent you from playing.
Resist the urge to pick and peel.