I'm 21, in college, but am not running for the team. I still compete and have been somewhat competitive on the local level (1:56, 4:15, 8:33 last indoors), and I'm hoping to continue to PR this year. However, track is a long way off, and I'll probably only race twice this fall with my last race being at the beginning of October. That leaves over 3 months between xc and the first chance to race indoors. I'm considering running a marathon in late October to mid November just kind of for the hell of it, running a decent effort but not all out. When I'm in shape I regularly do 17-19 mile long runs at between 6:15 and 6:45 pace depending on how I'm feeling, so I figure I could run a marathon in 2:45 or so without it wiping me out. Now I realize running a marathon makes no sense in terms of training for winter and spring track, but I find it easier to stay motivated when training for an upcoming event. Would running (not racing) a late fall marathon hurt me at all?