What are your goals? 800m? 1500m? 5k? 10K? half-marathon?
You mention 16-17 minutes for a 5K is your current level.
Are you trying to break 15 minutes? That is a worthwhile goal, especially at 35+ years of age.
My HS coach trained under Dellinger (and Bowerman) with the Oregon CC team during his graduate studies. I think the year was 1967. We did the Lydiard training in HS. I read "No Bugles, No Drums" in HS, which is Peter Snell's book. In college, I read Percy Cerutty's book, which I thought made it easy to understand why Herb Eliott quit at 22 years of age, although I don't think that was the goal of the biography. I also read Murry Halberg's book.
The leading distance athletes were people like Emil Zatopek in the 50s and Ron Clarke in the 60s. Lydiard becomes dominant, but Snell was an unusual runner who responded to the over distance with a minimum of injury. In 64, he was injured and had broken from Lydiard, so that Lydiard predicted John Davies would win the 1500m at the Tokyo Olympics. Snell won. Snell did a long 22 mile run once a week on a trail, just as he had when Lydiard was coaching him. I don't think there was much pavement on this trail, but Snell's focus after the break from Lydiard was more speed, less distance base.
Lydiard is based on the two racing seasons that NZ and Australia can enjoy. They have a mini-peak in late DEC, then during JAN - MAR they can race overseas and above the equator indoors (if good enough), or at home if not good enough. Afterward is another base period, then the racing season above the equator.
Lydiard thought that long, slow distance built up capacity for intervals later in the season. It involves systematic increases in tempo, while reducing the week's mileage.
For tempo runs in HS, we would often do "Lydiard" fartlek, which was long builds to a fast pace, sustained, then slowing down, which we would do several times in a 6-8 mile run. "Homer" fartlek was a good pace (6:30 - 7 min per mile) with stopping and doing several short sprints, then repeating.
When peaking, it is all about racing and intervals, which can only be sustained for a few weeks, and Halberg discusses this problem when racing Herb Eliott in Europe. Halberg said that one day the runners did a hard 15 miles (about 5 min pace) during this time over in Europe, and this seemed to reset the base and they could continue very fast intervals and racing a bit longer. This run included Herb Eliott
Lydiard is not about continued slow runs, and I don't see the point of 9-10 minute pace, except for the reason mentioned in another post, which is that is serves for general fitness for the members of your running club.
Gerry Lindgren did crazy mileage, and if he had backed off some, maybe he wouldn't have injured his ankle and would have won the 64 Olympic 10K.
Jim Ryun trained hard.
Other high schoolers were doing crazy mileage.
Kenyan distance runners (then others) came from a background of crazy mileage, but
Kenya eventually was rife with runners on PEDs--still is, but that does not exempt the other African countries who mysteriously produce such phenoms, nor China's women runners many years ago who were both forced onto drugs and forced into extreme training. The Soviet bloc countries had PEDs are part of the athletes training tables.
So...why are you running 13 miles. In high school, our Sunday run was 1 hour at about 6:40 pace; so about 9 miles. In college, we capped our long runs at 10 miles, and this is standard. It is true that I did them all under 6 minutes per mile in college, but that is also standard.
Years later, I made the mistake of doing 100 mile weeks. I lasted 6-7 months, all under 6 minutes. Then an injury from all the mileage, which I could have run through, but I was wise enough to stop and never exceed 50 miles per week again. Once the body breaks down from the mileage, it never really heals and will break down again.
I was not a good distance runner (middle distance when younger), but in my late 20s I did run under 14:50 for 5K and 30:12 for 10K, 51:28 for 10 miles and on a training run I did 5:10 pace for 12 miles before slowing down the last 3 miles for 5:15 average for 15 miles. Yet even I think 13 miles at 6:30 pace is excessive, especially once a week, unless you have some long race in mind.