I usually run 50-60mpw in the offseason and drop to 20-30mpw in-season (coach LOVES speedwork and insanely hard workouts). Predictably, this hasn't really been working in my favor, so this offseason I've been running 20-30mpw with a lot more supplemental work to get at least one season in when I can peak right. I still think that Lydiard was right and mileage is probably the most important part of running, but it seems like my work is just going to waste when I can't even run my 10K tempo pace in most in-season 5Ks.
Here is a typical week of my normal offseason:
Day 1: 9mi + 6xStrides
Day 2: 6mi tempo + short hill sprints + body weight strength training
Day 3: 9mi + short hill sprints
Day 4: 9mi + 6xStrides
Day 5: 6mi fartlek + short hill sprints, weights
Day 6: 14mi
Here is what I'm doing now:
Day 1: 4mi + 6xStrides, short hill sprints, jump rope
Day 2: 4mi tempo + 50m sprints, bodyweight training
Day 3: 6mi + 6xStrides, short hill sprints, jump rope
Day 4: 4mi fartlek + 50m sprints, bodyweight training
Day 5: 4mi + none
Day 6: 6mi + weights
Weights include floor press (just benching on the floor), deadlifts, overhead press, bent over rows, pectoral flys, half squats, ab rollouts, and lunges. Bodyweight includes pushups, pullups, one legged squats, and a bunch of ab exercises. It may seem like a lot of work, but I rarely spend over 1 hour and 20 minutes in the normal offseason (excluding the long run, which takes 1 hour and 40 min) or 1 hour in the 'new' offseason training. I just run and get straight to the point with the additional exercises, and to be honest I have to in order to balance school with my extracurricular activities and getting 8 hours of sleep.
I'm usually around 5'6 130lbs, and I found that with miles the strength training didn't increase my weight but just made me really lean. But after maybe 5 weeks of what I'm doing now, I've gone up to 5'6 145lbs. I'm still just as lean (still have abs), but my back and chest looks a lot bigger and wider. I know that there are many heavy/muscular runners that have success in the sport (Alan Webb, Chris Solinsky, Peter Snell, etc), but at this rate of growth is it just too much?