My fastest strength gains were made during a month block of fingerboarding last winter.
Depending on what you're doing at the wall you could alter your fb session accordingly.
So, if you're getting to the wall 2-3 times a week for routes/circuits, then I guess you'll have time for 2 or 3 decent fb sessions. In a week where you just get to the wall twice, it might be worth doing a more enduro repeater session e.g. 2 sets of 9x(7 on 3 off) rest 1.5-2 mins between blocks, and plenty between sets.
But, I reckon 2 or 3 enduro sessions a week is plenty, so the fb might be better spent doing higher intensity stuff. I found 1 or 2 sets of 5x(5 on 10 off) with 2-3 mins between blocks to be pretty good for max, and more satisfying than max hangs, which always feel like a cop out to me.