For me, it varies wildly due to a multitude of factors. Basically I adjust it upwards or downwards based on testing.
Very generally, though, I increase the pump time by about 30 percent between winter and summer, and I increase the SWG duty cycle from ~40% to ~50%.
I target an FC level of 4-6 percent, and I don't stress too much about it if it goes a little bit out of range.