As all of you have said in one way or another- this is really an individual thing. A lot depends on what you do off the bike, the weather, time of year, family etc.
As for me, I generally do at least 2 metric centuries (62.5 miles?) a week plus an early morning ride before I work that is (because of time changing morning light) a little over 10 miles. However, I also work out at the gym 1-3 days a week in the morning before I go to work. I consider my gym time as strength training for my cycling which is why I mention it here.
I do think having goals are a great way to keep you going and to help focus your efforts to the end result.

