You should confirm that by monitoring the thermals when you are experiencing this problem.
Incidentally, the text you quoted in the OP was written by me based on: It's a burning phone - #37 by dos so you may want to review that topic too.
Based on that I guess it is also pertinent to ask what else the Librem 5 was doing at the time.
Cycle Life may not be the only consideration but putting aside the question of whether you want the potential of sacrificing your Librem 5, is it even possible to adjust that threshold? Maybe there is some i2c incantation but you may need to read the datasheet to find it as @dos may be reluctant to encourage you in this direction. 