How long can I leave beer in secondary?

I am working on trying to keep the supply up with the demand around my house. I have a 4 tap kegerator and am always struggling to keep it full. I travel a lot and being away from home can put a damper in the beer brewing. I have two 6 gallon carboys and three 5 gallon carboys. I was away from home for two and a half months and am finally starting to get caught back up. Anyways, I was curious, how long can I leave my beer in a secondary fermenter before it gets bad? A month? Two months? I'm hoping to be able to empty a keg, and immediately move a batch from secondary into the keg. Thoughts?

a long time at room temp and stronger beers even longer. I left one in a closet for 7 months and it was great