Training 15+hrs....taper for HIM?

One week where the volume really drops down in volume can work well. Especially if you do next to nothing the few days prior. I've come to like 3 days of this with an easy 30 min run usually the day before. Maybe a couple minutes of that near race pace to wake things up, but that's it. I really hate how I feel these days, but think it has done a lot of good to take the time pretty much completely off.

The weekend before can still have a ride and swimming near race volume. Run a bit shorter. Hopefully 8 miles or so isn't an issue.

Two weeks out has been nice to put in a sizeable brick to help with pacing. The basic part being a bike similar in size to the race, and for this, about half the run has been good. I've done a shorter run before the bike as well, but this could go either way (or swimming is a possibility if logistically feasible). The bike and 2nd run are at or near expected race level.

Recover from this and concentrate on workouts for honing in race effort more for this week. Maybe slightly reduce volume here, but that's up to you. These efforts would be things like several 400's in the pool to hone in on race pace. Or a few 15-30 min blocks in a bike workout at race level. Runs with intervals at race level (HIM pacing). 1/2 to 1 mile on and easy pace recover has worked for me. Some might go up to a couple miles. This is more for familiarity than with fitness gains. You can start doing some of this the week before, actually. Watch the spacing between harder workouts more as you will want to recover well between them.

Yes, this is kind of backwards in the order, but you do want to start thinking about right before the race more than farther away.

I think that it depends not only on the next 8 weeks at 15+ hours, but also the past 8 weeks or realistically even longer.  What kind of volume have you been doing?  If you're already consistently training at 15+ hours then your body won't have as much fatigue built up as say, if you have been training 7-8 hours per week and want to do double that every week for the next two months.

In my experience, if i'm not at the end of a significant build, I don't need much taper time.  However, currently i'm nearing the end of a build that has taken me from around 11 hours/week to 14 hours/week and have a race on May 6th.  I'm darn tired right now and i'll probably take a whole week to taper for this HIM.

x2

I'm training about 15-16 hours per week in the peak phases of my HIM training...which totals up to about 7 weeks total when all is said and done...not 8 weeks straight though.  My body is very comfortable training at 11-12ish hours per week, and if I was doing 12 hour weeks for 8+ weeks, then I wouldn't need that much of a taper.  But I do need a good taper following 15+ hour weeks...simply because my body isn't accustomed to it.

I'm doing an Oly 2 weeks before my HIM this year, so my taper is going to be a little weird and unconventional.  Still haven't figured out exactly how I'm going to do it...but I won't be doing 15+ hour weeks in the 2-3 weeks before the HIM...that's for sure.

Very true.  Add to the fact that people define what a taper is differently, and it gets even more mudded.