Random idea (something I have not done but just thought of)

Go to Last year’s IM race results For your race and go down the list of athletes...look for someone who finished top 5-10%, look them up on Strava...try to find the one with the longest history on Strava...take an hour and write down his / her workouts over the period leading up to the race...

Do that a few times and see if you find a trend

+ reading
+ archives on Slowtwitch

= maybe you can get smarter and faster?