I’d get in the habit of running most days with a schedule like this:
M = 4
T = 9
W = 12
R = 9
F = 4
S = 10
S = 2-3 hours
Then I would race when I wanted to. I would try and get faster in the summer by incorportating intervals on Tuesday and a 5k tempo on Thursday. If I was racing on Saturday, I would skip the Thursday tempo.
Occasionally I’d do a hard 10-15 miler on Saturday and run easy for an hour on Sunday. The change up is good. I’d taper three weeks out and have a good race come marathon day.
Run hard and run easy. Take a day off when needed. If really tired on hard days don’t worry about running a little slower. The key for me is the long run days. Get to the point you don’t even hesitate to do a 20 miler. You can’t compromise the long runs, this is were the rubber meets the road.