I can't argue with erring on the side of caution. But LiPos don't just light-off.
It's typically (crash) damage or trauma, an external short, or improper charging.
My local Hobby Shop has hundreds sitting on shelves and has for about 15 years.
Yep, for sure, with both of my LiPo discharges, they were damaged from acro crashes (like head-on into a tree type of crashes). The catastrophic discharges happen when air mixes in with the chemicals inside the LiPo, so pretty much every time the surrounding cell membrane has to be punctured in some way to initiate it. I think even in the cases of over-charge/discharge, the insides expand enough to pop the membrane. Maybe a short burns through?
One went off immediately in the field right after the crash. The second (the garage fire one), however, was damaged but not enough to discharge right away. When I got it home, I was inspecting it and wiggled the battery lead, which I guess opened up the membrane and it went off in my hand. I had to drop it, and it caught a little mat on fire. Fortunately, I also have fire extinguishers in the garage, which put out the mat (but most common fire extinguishers won't put out a LiPo, they need a special chemical one that is pretty expensive).
As I said, a Phantom battery has the enclosure around it, as well as being in the craft, so not likely to get the same damage as a smaller quad LiPo that's just hanging off it. Unless it gets dropped on a concrete floor or something.
Yes, I'm admittedly overly paranoid. But if I can get someone to think a little about LiPo safety and save them an incident, I'm happy to get laughed at.
Cheers,
Paul