Take this anecdote for whatever you want -
I'm a middle distance runner. I was injured most of last year and the beginning of this year and only started running back at my previous mileage levels this summer. So then this fall I got back into a regular routine, two workouts per week.
With this thread in mind, I decided not worry about long runs, since malmo is calling them the icing on the cake. Since October I've been running regular 50 mile weeks, so a 25% long run would be 12.5 miles. 20% would be 10 miles. I've probably only run more than 10 miles once or twice over the last 15 weeks. Usually I'll try to get in a hard 8-9 mile run, but honestly I don't think of it as a long run - it's not even taking me an hour!
Anyway, the point is that cutting out long runs (or at least the dogmatic idea of a weekly 75-90 minute run) has made zero difference in my race performance. Actually I'm having a great winter, indoor pr's at 800, mile, and 3k (and I think I'm in 5k pr shape too, but probably won't run one).
I will probably bump up my mileage and do some longer runs this summer, but once next fall hits and I'm back to doing several hard workouts each week again, no way will I try for a 20-25% long run.