I think I've been pretty lucky with my collection so far. I have dealt with some problems (mites, tapeworm,RI) but everyone is still alive and doing well.

The more you collect the higher your chance are that something will go wrong. Ball pythons are pretty hardy snakes. My first one survived the first 4 months with me as I was doing everything wrong and now she's doing great. She's been breeding for me, but I don't know if she's going to ovulate anytime soon.

I learned about QT before I had any serious problems (mite out break in my QT room >_<), the RIs I have dealt with were very minor and easy to clear up and tapeworms are pretty easy to treat. Overall, I would say I have been pretty lucky too.