Let me start by saying that different things work for different people. But my observation is that many middle-distance runners are being trained like distance runners, and their development is limited as a result.
This was really brought home to me last year when I re-read the original "How They Train," Fred Wilt's 1959 compilation of training routines from the (mostly) 1930s/40s/50s. The times from the distancemen he profiled--many of them truly elite runners, including Olympic champs--really don't hold up today. Yes, tracks and shoes have gotten faster, but not *that* much faster. Meanwhile, some of the 1500/mile times, and especially 800/880 times, among those he profiled stand up pretty well, and would be competitive in many meets today.
The training routines he detailed featured, especially for American runners, day after day of interval track work. Those didn't work so hot for distance runners--a 9:00 two-mile was considered truly great--but the half-milers, especially, did pretty well with it.
Many college and high school teams are coached by distance runners and tend to have the same training pattern for everyone from 800m guys on up: long repeats on Monday, recovery distance on Tuesday, shorter reps on Wednesday, distance on Thursday, say. (And even off-season/pre-season training is similar for them all: lots of easy distance, little or no speed.)
This might be convenient for the coach--easier to keep track of one's athletes--but is that the best way to go? Why not have the half-milers on the track Monday and Tuesday, recovery day on Wednesday, then back on the track on Thursday, say?
Anyway, coaches, what's your opinion? Do my observations here match up with your experience?