In reply to mountain_jay:
Personally I try very very hard - on each individual hang. I always have a rest day the day before (as I'm scared there's little warning when a finger pulley ruptures, and it seems the safest option).
But conversely I add incremental weight / volume / smaller holds very slowly, like never more than 2 or 3kg every other session for a given hang.
My first workout in a finger boarding phase I'll start with weights that I can get through the BM5A workout (1 set only) without failing a hang. I take off weight for the crimps using a pulley to achieve that (terrible at crimps). I add about 15kg for jugs and 10kg for 4 fingers open (just by way of example, obviously everyone's differnt).
By about the 3rd or 4th session I've tuned up each hang by adding weight/ reducing assistance so the 5th and 6th reps are in doubt: half the time I fail at 5s or so and half the time I can just hang on to 7s. If I get to 7secs for every rep and write "not too bad" in the diary, then I add 2kg next time. Most entries say "really hard" or "absolute limit"
Those hangs I keep the weight the same.