I have read the posts and forgot most of what was said so will probably repeat some great advice. I would train like a 5k runner at about 40-50 miles/week most of the time and maybe drop down to 25-30 during the razor sharp, pucker-your-external-sphincter, get-r-dun, time of the season. I ran 2:06 during marathon training when I was 37 and was running around 65 miles/week. But, a few weeks before the 800 "fun race", NOT!, I ran a 8 x 200 with 200 jog workout on the track withh the 200's in around 32-34. 10-14 mile long run on Sunday morning during other folk's church is a must!!
Once that gun goes off, you gotta turn into a entirely different person and when the race is over, you are your old normal self again. If you ain't got two personalities, a nice guy, humble, help the little lady across the street personality vs. the rather fight than f---, take names at the half way point, thinking-about-your-best-friend-who-still-may-be-stuck-in-a-damn-prisonhut -camp,in north vietnam, attitude, don't waste your time racing.
Ho hum!