Longest Run Ever - 21 miles

So I was planning to get in a long run today.  I took yesterday off and had a wonderful pasta dinner last night with peanut sauce and tofu.  Homemade by my loving husband!  I was feeling primed and ready to go running.  I was thinking that I would go to the end of the path and back.  But then I had an idea in the first half mile.  Maybe I should really test myself and see what I could do.  My next scheduled race is not until May 6th and I signed up for the half.  My youngest had a special mother/daughter brunch the same day so I was going to run the 13.1 and then go to brunch.  But now she is double booked with a soccer game and brunch.  I think the game is going to win out.  Well within the first half mile I started to wonder if I could up my 1/2 to a full!  It is my home turf race.  The full literally goes by half a block from my house.  Then the question became could my body do it?  Well on today's 3:33 odyssey I averaged 10:10 miles for 21 miles.  I had my running bottle with me, a pack of Clif Shot Blocks, and I bought a donut at mile 13 for fuel and so that I could use the restroom.  It would be a real effort (huge understatement) to finish the final 5, especially as I ran past my house, but I just might do it! All comment welcome!