Originally Posted by BioRage
Keep a cheapo AEG for backup and winter, and a gas for cqb and summer outdoors
I did that for a while; never went to the backup. I now carry a spare complete bolt carrier (NPAS and all), and a spare trigger pack -- neither of which I've needed as of yet. But short of my gun getting run over by a vehicle that pretty much covers anything that could break during a game. Otherwise if a mag goes back, I'll toss it aside and be down one mag.
I also don't play often in winter, so I haven't tested it in extreme cold, but in cool/cold weather MAPP gas works well. There are other threads about it by people with more experience.