Varies a lot. Most of my flying is self funded, with the odd random work trip thrown in a couple of times a year.
I find I tend to go in blocks, I'll do 4 or 5 flights in a couple of weeks, then perhaps 4 or 5 months till the next group.
But, perhaps the longest would have been in the late 90's, probably went 4 years without flying. Mostly due to work commitments. (which obviously didn't involve flying). Made up for it from 2000 through till 2007 with a lot of flying. Heck! If I'd only known about SC and FF points then! Only been in the last 5 or 6 years that I have discovered the bug.