LiFe's are very sensitive to being overcharged or fully discharged. They are more physically tough than Lipos, but that's it. That said, I have a couple of puffed ones in planes I fly now. They both cycle fine and maintain voltage fine, so I've kept using them. I saw something a while back that said early Lipo puffing was caused by water vapor that got trapped inside the cell casing and didn't affect the battery's performance. I have to wonder if that's the same situation with LiFe's as well.