So my marathon training is all based on doing my longest run one month away from marathon day. Leading up to that super long run and following that long run, I'll add/subtract 20 minutes from my run length every weekend. So I'll do a 100 minute, 120 minute, 140 minute, 160 minute, 180 minute, 160 minute, 140 minute ... you get the idea. It's like a bell curve of run lengths.
Here's how it mapped out. Not too shabby.