So here's the deal. I'm playing the current weekly challenge: ratling necromancer with H--- and ^+. It's a subsequent playthrough, so I'm mostly testing strategies rather than going for max points.

The character's got a shitty Le and skill dice values, so I've decided to see how much I could get out of training him on (the rather numerous) traps. The idea was to give him time to passively appraise the inventory gathered so far and execute burden-based strength training while boosting First Aid by repeatedly triggering traps and healing up (via FA, then naturally). I'd only used Knock thrice to open some doors and Frost Bolt twice to get rid of some pit vipers before the trap training. So a total of five spellcastings, and 3 or 4 successful attempts to read a book. I'm level 2 with 273 xp total, so I only leveled up once.

I started my experiment with a spear trap at around turn #4000 and moved on to a nearby pit. Drop, FA, climb out, w5, rinse and repeat. I kept receiving small Concentration increases for over 60k turns (maybe even 70k!) despite being at full PP the entire time, and trained it this way from around 70 (3d3 die IIRC) all the way up to 91 (1d5 die).

Just how deep is this training buffer? Is it supposed to give out increases for such a long period of time?