"Champions are everywhere; all you need is to train them properly..." ~Arthur Lydiard
I don't know, 3 slow miles a day on the treadmill seems to be working out for me right now. Just trying to keep one step ahead of the man from the glue factory.
I wish you the best on your twelve miler ever cranium. Of course you can, of course you can. Just remember...take it easy, hydrate, take your gu with you and don't talk to strangers.