I have done this and fermentation takes off in few hours. Just make sure you lower the temperature to the correct temp. of your yeast you are using. And I've had no off flavors doing this.
Yeah, the first time I had Sam Adams Boston Lager, and Sierra Nevada pale ale I thought that they were so malty and hoppy.
Now thirty years later I find them pretty tame.
Got a new Cereal Killer last year, never used. I'm just waiting for my seven year old Barley Crusher to die, I must be one of the lucky ones to have it last that long!