Well maybe not bullet proof, but at least R/C tough. I got tired of putting new fans in my conversions only to have them only last 20 minutes before they puke up their internals components. The smaller fans weren't so much of a problem, for me at least, it was the larger size like the 40mm fans were the problem. So I decided to do something about it. Here a couple of things you can do to make your fans tougher.
Here is the most of the stuff your going to need:
Small gauge multi strand wire
Electrical grade epoxy or substitute (I used a 3M's part # DP 270) I got this at Mc Master Carr $11.13 http://www.mcmaster.com/
Hand plunger for the epoxy, as it doesn't come with one. I got this at Mc Master Carr also Part # 74695A27 $1.15each