I'd only give up on a project if it went from being fun to being work. I enjoy the time I spend with my animals. I commute 2 1/2 hrs a day, work 10 hour days, have a wife and newborn, but I STILL find the time to take care of my animals because I enjoy doing it.
If I ever thought to myself, "man, I don't want to clean all my snakes cages, weight them and feed them today" I'd sell every snake I have. Buuuut, when it comes to my rats, now that's a different story. They really are work, but worth it.