Marathon Finishing Times?

FYI, in 2006, the average marathon finish time for females ages 25-29 was 4hrs 58 minutes 41 seconds, which is a pace of 11:24/mile. (See here for more of the breakdown.) We ran our 10 mile run with an overall pace of 11:10/mile, and that actually felt pretty slooooowww (but all these training pages keep telling us to run our long run slow!) Using this Race Time Equivalent Calculator, our marathon time would be something like 5 hrs 16 minutes. When I enter in our 5 mile run from yesterday, which we ran at a 10:33 pace (because we started off slow), we get a marathon projection of 5 hrs 10 minutes. When I enter in an average 5 mile run from last week with a pace of 10:23, it goes down to 5 hrs 6 minutes. Why all the info? Weeeeeelllll, I was just thinking that IF I were to make a time goal for running the marathon (and I'm not saying that I am!), I think it would be to break 5 hrs, or to be right about average. It might seem silly, but to me, qualifying as an average runner is (would be?) just plain awesome!