Originally Posted by kvh
That is all perfectly normal. That yeast is the whole reason you moved to secondary. You could let it sit there for 3 months and it wouldn't affect the flavor of the beer.
Relax and have a homebrew.
Well thats really not true. After a period of time the yeast will eat some of the compounds within the trub which "may" produce off flavors....however these off flavors can be considered favorable. Especially if you are a fan of "real" ale. The longer your beer sits on the yeast cake the more it evolves.
The answer to your question Cos, yes that is normal yeast slurry and trub, you are fine keeping your beer on that cake for at least a month without any off flavors. And even if you left it on it for longer you will still have perfectly good beer, some would suggest maybe even better.