The more frequently you brew your various lager recipes, the more you will figure out how long each of them should be lagered best. For example, I brewed up a new recipe in Feb for a traditional bock that I have not brewed in about 5 years. I had lagered it for about 6 wks prior to entering it in a local competition where it took a gold medal. This week (about 3 months of lagering in the keg) I have found that it has reached its peak and tastes absolutely awesome (even better than when I originally had it judged at the comp). So now I know the next time I brew it where the sweet spot for lagering is.