It is a long time and it gets frustrating when there is significant time where there is flailing with no visible progress.

I have had long bug hunts (~a month each) and witnessed ones that took much, much longer. But the longest one I witnessed was drawn out because reproduction was initially unreliable and could take weeks to months. Thankfully, reproduction was by letting a box sit in a corner while tje people involved moved on to other tasks. This kept everybody sane.