Been running for a long time but...?

The quality of your running only matters if you are running for a specific reason, such as competition or fitness. If you are running competitively of course you want to see a increase over time in performance. But, if you are running for fitness just to keep in shape, its still getting the job done if you are working out your cardio. Try running with a high heart rate to see better fitness results.

If you are trying to improve your time for distance running, quality is a definite necessity.

I run cross country for my high school and I'm on varsity. My workouts consist of 3 to 5 mile runs during the week, 4 times a week and either Saturday or Sunday I'll run 6 to 7 miles. Sure getting the miles in will make running easier but if you aren't setting a certain goal when running those miles you won't improve.

This is what I do and what I am suggesting you try:

-Go out and run a weeks worth of workouts like what I do above^ and make sure you time every run

-The workouts during the week should all be finished in the neighborhood of the same time and then your longer distance run is just about getting the miles in, in a reasonable time

-Next week you should shave off at least 5 seconds from each run

-Continue shaving off that minuscule 5 seconds from every run and you should see an improvement

In short, increase running distance. Not only that, but your time as well. Go faster, stronger, and longer. That's it. Eat well, and continue running. You should be fine