At least 1 year. My CC Amarone is just becoming fantastic and that one was started in April 2005. Actually, it was very good last year, but now is bordering on the sublime.
All my grape pack reds need lots of age. I've still got all the RJS winery series from last year (brewed from about Februrary through april) in the carboy, and really should start to bottle them I guess, since they are over a year old already.