Ok, I'l admit I never go below test depth (assuming that test depth is what a pointer is contlinuesly pointing at ~110 meters in my depth meter). I had some sudden sinkings with version 1.00 and I decided that fleet boats aren't u-boats and avoided 3 digit depths from thereon! (Of course the sudden sinkings could be due to a compromised hull but back then I didn't know if/when my hull was compromised in the 1st place!

). So not going beyond test depth maybe a reason for my next question which is:
Does "compressed air" ever get consumed by "normal operations"?
Remaining at 40 meters, for 10 hours, (stationary) doesn't affect it! [edit: Ok maybe to shallow...]
Surfacing, at 0 speed doesn't affect it!
Blowing tanks probably would, but haven't done that for a long time!
Or is it just a doomsday indicator such as "We lost our batteries, we lost our air... let's put something on the gramophone and wait for the grim ripper. It's harvest time!

"
Playing: SH4 1.4 / no mods.