Newer lipos "should" never go nuclear on you, but better safe than sorry I guess. Never buy cheap lipos though, or you'll find out why they were such a good deal.
I have seen one modern lipo explode. We were at Battlefield in Calgary, and it went nuclear while in buddies G36, a Tokyo Marui I think. Anyways, they got it out and saved the gun, but just in time watch it burn up on the ground. The battery brand was either Firefox or Airsoft something (white label). We had just switched most of our Systemas over to lipos, and now all of our batteries are pooched. I mean literally near every single one from a large group of them. To be fair, the charger and/or charging method could be suspect. What I've learned? Buy high quality lipos only, and but a high quality balance charger only. The IMAX B6 seems to be the preferred one in airsoft. Always store and charge your batteries appropriately. If not, or if this method is too expensive, then stick with NiHm or NiCd. They do work, they're cheap, and they don't explode.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē