I have 9. One is star san, as I dont feel like getting a different wrench for one post out of 18. So it always has star san, which is really useful.
I am planning on bottling half to all of my wheat beer this summer. I like the carb levels high and I do not have the ability to do that on one of my 4 taps with my current setup. ( would need 2 secondary regs and a longer beer line for the wheat, may do that later). Plus bottle conditioning wheat gets more wheat in suspension during pour, which accentuates the hefe taste I love.
I would like to add 4 more kegs for pipeline/age. I will likely bottle more as my kids grow older. I like having bottles, but time is higher priority right now. I clean a group of kegs at once, then leave them sealed after pumping star san through them. When I am ready to keg, it takes little time (sanitize outside, pop the top and rack in). That allows me to get it done in less intensive chunks of time.