I remember there was some discussion if low reverse currents can damage a bipolar transistor. I got a new toy (HP 4142B with 3 SMUs) and did some quick testing.
It seems that even 1uA reverse current starts to destroy the transistor. Here's a graph that shows hFE as a function of amp-seconds from the base:
I also did an another test with 0.1 for 2000s and 1mA for 2000s:
The reverse voltage increased during the test from 7.5 to 7.9V
The quick test was limited to 2000s, i.e. 2mAs, but I'll do a longer run to see if the detoriation depends on the charge only or does current have some effect.
(Unfortunately transistors _were_ harmed during the tests.)