I agree with Mongrel. Here is some info I got when I was looking for info on best practices for Lager beer although I can't remember who I got this info from:
Lagering Time - How long to lager is a matter of some discussion. Light American lagers are typically held near freezing for 10–20 days, while some strong German doppelbocks are lagered as long as six months. For medium to high-gravity beers, Greg Noonan — brewpub owner and author of “New Brewing Lager Beer” (1996, Brewers Publications) — recommends 7–12 days per each 2 °Plato of original gravity. (One degree Plato is roughly equal to 4 specific gravity “points.”
. For lower gravity lagers the time is reduced to 3–7 days. According to those guidelines, a 1.064 O.G. German bock should be lagered for 112–192 days, while a 1.040 American lager would be lagered 15–35 days. The correct temperature for Lagering should be between 33–35° F (0.6-1.7° C). This temperature range is the same for lagers or ales and should last for 1 month minimum.
Fortunately, brewer’s yeast is capable of reabsorbing the diacetyl and reducing it to a related compound (2, 3 butanediol) that has a far lower flavor threshold. However, this requires warmer temperatures, around 60–70 °F (16–21 °C, than the optimum conditions for clean lager fermentation. The solution is to raise the temperature for a brief period (24–72 hours) after the yeast has nearly finished fermenting the beer.
Diacetyl Rest - For homebrewers this typically means letting the fermenter warm to room temperature for a couple of days. Not all lager strains produce significant amounts of diacetyl, but unless you have previous experience with the yeast you are using, it is best to perform the rest anyway, as it does no harm. Conduct the rest in the primary fermenter in order to maximize the yeast population and quickly reduce the diacetyl. Raise the temp of the carboy and then bottle. I typically raise the temp toward the end of fermentation anyways to help the yeast clean up a bit. Raising the temp will also wake up the yeast a bit so when you rack on your priming sugar, they are ready to go to work