I usually suck at stealth in games, so it seems strange that I managed to do this so easily when others have struggled.
The game basically shows you where you need to drop the bananas to lure them away with the collapsible platforms dotted around... shoot the support with an arrow to drop the...
I don't think it's related to time... they seem to spawn every time I walk through a spawn location... if you avoid the spawn locations you probably won't see them at all.
As for the stealth section... you don't need to kill them, you can just go around... I personally didn't kill any of them...
They always seem to appear in the same places, so if you're having trouble with them, you could probably put a stamp on each location and just go around.