The bottom line is the n52 left very little on the table, or atleast the 255 output versions. The ones where you add the 3 stage intake and tune are pretty good gains but otherwise just a tune really leaves a hand ful of HP on the table. I had an n52 back in the day and was a nice little engine, smooth and sounded great.
As far as adaptions, within 4 dyno pulls of WOt a car is adapted so not even close to a month, multiple tanks or even 30 minutes. Do a few hard pulls on the dyno between mods and your computer adapts.
If it took a computer months or tanks to adapt it would obviously be unable to do its job as the job of adaptions is not there for us to add mods to and make more power, the computer adapts to ever changing conditions such as heat, load, octane/detonation sensing etc. Changes are extremely quick.