Your worldly view...and I know by that you mean that it's typical in America that a work week is 40 hours. Interestingly enough, it didn't use to be. Nor is 40 hours typical in some other countries. Many more hours than that are often put in.
Now let's look at it the way we should: biblically. Could you tell me just what the Bible says is proper time for a pastor to work? Because that is truly what all pastors should be concerned with, not with what the secular world puts down as full time.
Just FYI, even if a pastor "only" puts in 20-30 hours, pastors are always on call. Folks get hospitalized, they need their pastor. Folks die, family needs their pastor. Folks have wayward kids, they need their pastor, etc., etc. IOW, a pastor might only "put in" a certain number of hours, be he is ALWAYS on call for his people. That's way better than putting an hourly requirement on.