I'm 26. Age really isn't a factor. Not as much as the general public makes it out to be. You should see the times "Masters" guys are running. Hopefully I break 2:40 for the Marathon this year. Ran 2:47 last summer. PR'ed. Training is going well. Typical week for me.
Wednesday(start of the week, each training cycle I pick a random day.) - 60 minutes
Thursday - 80 minutes
Friday - 60 minutes
Saturday- 120 minutes
Sunday - 30 minutes
Monday - 60 minutes AM, 30 minutes PM
Tuesday - 30 minutes
I'm at 65 miles per week right now. Will build to 80-90mpw. I go 10 days/day off then 7 days/day off and rotate back and forth.
Type in Arthur Lydiard Training. That's the bible. There are different running/training philosophies but Lydiard is to running what Phil Jackson is to basketball.
What she is referring to is common sense. The conditioning phase. Usually people have to learn by trial and error. But you can't sprint a 5k or 10k or Marathon. If you've never ran 10 miles, you aren't going to run it the same speed as whatever you normally run in distance. It's just common sense. First time you do a "long" run, physiology speaking you will change. Everything about you will change.