After XC I want to move to longer distances and focus on longer stuff. I am a 17:3x 5k runner so obviously shorter distances are not my forte, but I always have loved long runs and I can hold speed for long times but I can't drop the hammer for these quick little 5k races. Is 18 too young? My coach discourages it greatly and says long runs and marathons are bad for guys in high school, and really for guys who are under mid 20s. I think marathons could be my distance that I can have some success in because I have run a half marathon in 1:18.
Is it as simple as (when starting to run marathons) put in a ton of easy miles? Like starting in November work from my 50mpw to 80-100mpw all easy to build the aerobic base then tackle some tempos and progression runs?