Getting old, been gradually throwing the harder workouts out of the toolbox to avoid injury.
I've been considering completely discontinuing scheduled harder workout sessions and just running a bit harder whenever it feels right during a daily run or long run; no adding up or tabulation of M,T, VO2, steady, hill sprints, R....
I'm 57 and run about 50-60 mpw, year round.
I'm interested in any experience with the above approach.