Age 47.
I run for about an hour a day every day and ave about 7 min pace, though my ave pace is still dropping (been running for about 1.5 years after decades of not running).
I don't do the hard easy thing. I think it's wrong (especially for older people). You get less work done doing hard easy rather than spreading the effort out, and you are always risking injury on the overly hard days.
I never steal from the future by running overly hard, so I feel about the same every day.
I either do steady state at 7 min pace for the whole hour, or mix it up by going slower for the first half or 2/3rds of the run (7:35 pace) then tempo run the last part (6:25 pace), or attack a hill etc.
If I am too tired the next day, then I screwed it up. Doesn't happen often.
Also, I do a lot of trigger point massage before I run to loosen up my hamstrings and calf muscles. No stretching though since I don't think it helps with anything.
After my run, I do nothing eccept drink water and eat something. I know I can come back the next day and repeat my efforts since I haven't done anything I haven't already done hundreds of times.
I mentioned I repeat my "effort" and not pace, since my pace gradually quickens for the same effort over a long enough time frame.
Perhaps it's not the best training method and maybe you can get an extra boost by going to the track and doing an "amazing" workout, but I say those "amazing" workouts end up being a negative since you are just gambling with injury and or have to essentially take the next day or two off to "recover". So while you are eventually sidelined with some problem from a workout, I am still moveing forward as always.