Yeah, some things are in high rotation - usually Gin, whatever decent one is on special so Beefeater, Tanqueray, or Bombay - but the rest is a built up collection, and as it's not my main drink, usually stays a while. It starts by just buying an extra bottle of something different when I went to the bottle shop.
So I go and buy my bottle of gin to drink, and also grab a fancy liqueur or something. My red wine collection is because the shops here often do specials for getting mixed half dozens and stuff. So if I'm going somewhere, I'll buy 6 instead of 1, and put the 5 on the rack.
The key is to replace what you drink plus some. So if I drink a bottle of gin one night, I'll buy more than a bottle of gin to replace it.