I counted by hand for teams with 16+ seasons who could contend with ERG so I might be off on this but
sorted by longest run but broken out by different runs, like BMG made NBBA (+1), demoted, promoted back (+1), demoted, promoted back and stuck around for 15 seasons straight (+15).
Lake Merritt Arrows (original): 18
Chicago Bulls: 17
Eugene Register-Guard (original): 16
Burlington Mountain Goats: 1+1+15
King Drive Ballers: 13+8
High Point Heroes: 13+3
Arizona Cacti: 12+3+5+1
Irvine Anteaters: 1+1+11+2+1+2
Delta 9: 10+2+4
Beware of Dogs: 7+8+2
we can see if Coco (looks like his new team is 'Black Light') makes it back to NBBA to start a really weird record/trivia contest vs. ERG and KDB
also I wonder if anyone has more D.II championships than Irvine Anteaters