After 8 months, an update. I never did get my sub 20 last summer. After my last post, I ran 3 more 5ks, never finishing faster than 21:02 in any of them. I did however run a half marathon PR in October at 1:37:27 and a 4-mile PR in November at 27:18.
In December I started training for a spring marathon, which is now only 2 weeks away. This past Thursday I ran a 20:36 5k the day after a 7.5-mile tempo run and 4 days after a 20 miler. Now I'm wondering what I could do on fresh legs.