The theory about Dan being in his 20's isn't very valid. The male voice reaches its peak in your 20's. Your voice drops significantly during puberty. However, the male voice levels out again with maturity. In fact, in most cases, the vocal range capability increases quite a bit.
As for the drumming on Spending Time: I don't understand why some of you guys are saying that it was obvious that his heart wasn't in it from the drumming. The drumming isn't very flashy, it is simple, but tight. If anything I thought that was the most mature sounding album Ozma has released in every way, including the drummer. However, I look forward to hearing Kenn's drumming on the new recordings.
-Brent