I have 5 and my keezer holds 4 and sometimes I will bottle half a 5g batch in 22oz and keg the other half. For some reason I like bottle conditioned beer.
I usually brew 10 gallon batches. Sometimes 5 gallons. Sometimes partigyle with 5 gallons strong & 5 or 10 not so strong. Usually the strong ones (Scotch Ale/RIS/BW) get bottled.
I think 9 5g, one 3g, and 1 10g. I'd like some more 5g. The 10g is too much of a space hog in the keezer so I don't use it for serving anymore. I think I should start using it as a fermenter instead.