I'm only familiar with Lager brewing from what I've read, I have no experience. That being said, I have never heard anyone recommend racking to a secondary before primary fermentation is done. The rule-of-thumb I use is to wait until I have 3 consecutive days of no change in my gravity.
I know with Ale, which ferments notably quicker than lager, that 7 days is a pretty small amount of time before racking to secondary. I would recommend, at the very least, to make sure that your primary is done by using 2 hydrometer readings over a 3-4 day window. 2 weeks is usually the fail-safe time used before racking an Ale to secondary. So brewing a lager, I would think that 2 weeks should be your absolute minimum. Anybody with more experience with lager, please feel free to contradict my assumptions.