It already is paying off.
Two weeks ago, ran 5k in 23:03 (7:08, 7:27 (14:35), 7:42 (22:17), 0:46 (23:03)), humid, rainy, went out too fast, not enough hydration.
Last week, same course but better weather, ran 22:38 (7:25, 7:20 (14:45), 7:07 (21:52), 0:46 (22:38), but with much better pacing and hydration. But still had a side stitch.
Throughout all of these past few weeks I've slowed down my EZ runs and can log them at 7 miles @ 62-65 mins. No watch checking until 3.5 miles in, and then again at the end. Even by doing these EZ runs your pace will STILL drop just by pure base-building.
Did a 5k today, on a slightly flatter course (but with less shade) and ran 21:34. Was out of breath for 20 sec. at the end but felt fine right after. Ran by feel: 6:52, 7:03 (13:55), 6:52 (20:47), 0:47 (21:34).
My main event is the Marathon but I just did these checks to see where I'd be at if I wanted to do a 5k. I'll resume base-building now for my original race, now that Ohio may lift mask mandates on June 2 and we *might* have a Marathon.