Comment by pengaru

Leaving such devices plugged in 24x7 unattended creates opportunities for such ambient conditions to develop unnoticed.

These mobile LiPo-using rechargeable devices simply aren't ideal for being left powered while unattended, day after day, year after year. All it takes are some sunny days with normally closed blinds left open and you may slowly be cooking that device you forgot about that Just Works but is a ticking time bomb after the 10th day it spent an hour in direct sunlight while charging.

AIUI the high temperatures are particularly damaging to the SEI (Solid Electrolyte Interface) layer, which is the layer preventing dendrite growth. If that layer breaks down enough for dendrites to grow, you're in internal short / fire-risk land.