Ya, the fish move in waves.
How long the bite stays in often depends on how many fish are in the moving school.
Sitting/fence posting at some spots can change from boring to frenzy and back to boring quite quickly.
Timing is everything.
I've given up on a spot after a while and often found out I should have stayed a little longer.
On the other hand I've also moved (more than a few feet) and intercepted, and had amazing days.
Having said that, there are some spots that will stack up fish and they turn off after dodgeing schrapnel for a while.