+1 at flar. At some point you just know what will work. I haven't posted a photothread in ages, but I would go out four or five times, take 20-30 images each time and put out a thread of about 50-60 images.
It boils down to subject matter and lighting. If you know the area, you know what you're looking for and you know when you should show up.
I would over-edit my threads a lot. I did take a break from over-censoring what was coming out of me in
this thread where I posted every picture I took in about 40 minutes of time and it might actually say more than one of my multi-excursion threads. For me it boils down to having something to say.