any amout of light thats not normall outdoor light star/moon wont change nothing, but indoor light leaks could stress your plant and make the hermie.
as for 12/12 i think 14/10 would be the most, then they would revert to veg, i veg in 18on 6off, and how long well I had the power go out and burn a
timer, well i didnt check on then for 3 days i was camping and shit, well i fixed the timer and thats all it took they reverted all bud productio stoped
and it took 10 days to get on track plus there was some weird leaves that came of it.