I do strides at the end of 80-90% of my easy runs.
When I'm doing doubles sometimes I do them at the end of both runs.
I think the only whole day I go without them is long run day, unless I'm feeling really good. Usually I'm too tired and decide they would be ineffective because of my fatigue.
At any rate I have a sweet kick (for a 30-min type 10k runner) and pretty good top-end speed (to be confused with leg speed etc).
I have only lost a small handful of races in the last 100. That isn't to say I haven't lost plenty of races much earlier on in the race, but if I'm still there with 100 to go I can beat the other guys with my PRs.
Take this anecdote as you will.