Doing a HIM during First IM Training

I don't know that it is that important.  For me, it was actually a confidence de-booster.  I had an awful HIM 8 weeks from my IM that actually shook my confidence and made me question how I could finish an IM.  My previous HIM had gone perfectly.

The arguments for it include practicing race day nutrition and pacing, as well as to break up the monotony of training, among others.  But on the other hand, if your training plan calls for a mini taper and recovery for the HIM, you will actually lose valuable training time just eight weeks from your A race.  Nutrition and pacing can and should be practiced during your long rides and runs.

So I don't think it's necessary but you won't be wrong for doing it either.  Just look at why you are doing it and what the value you are trying to get from it.

Best of luck, it is an amazing experience!

I did one - I liked the race simulation and getting the additional OWS in a race (I am a nervous swimmer).  It was even nice to practice aid stations on the bike which can be tricky to navigate.  It was a hot race in comparison to my IM and I did take a few off days around it but tried not to race too hard knowing that I would need to get back into training right away.  It didn't seem to have a negative impact on the rest of my training. It worked out to be a great confidence boost - I had a great IM. 

Plus, it's nice to race - training for IM is a bit of a grind in my mind and having a few races planned helps to break it up a bit and remember how much I enjoy the sport.

I have a HIM planned during my IM training as well....more like 12 weeks away, but I think your plan should work ok.

Since your HIM is closer your IM, I would think the trick is to get all the long rides & runs in, according to plan.  I find the taper, race, and recovery does interfere with training, but you really can't bypass these stages of racing.

It depends...

Are you a seasoned athlete that recovers well?

Will it bring more stress or joy to your life?

If you are injured or injury prone, racing 8 weeks out from IM may not be a good idea.

If you are older, it may take longer to taper and recover.

If you have been an endurance athlete for many years you will likely recover faster and if newer athlete you may take longer to recover and put a 3-4 week hole into your IM training.

To many factors to say yes or no without more facts.

Do it, or not. I don't think a HIM as part of the training plan is necessarily bad but I also think you can easily skip it. You have already done an HIM so you know about nutrition etc and how you feel going very long. However, the step from an HIM to an IM is significant so I don't really think it will help with confidence (are you really going to be more confident knowing you can do a HIM now? You already know that...). Personally I think you will get more from an extra killer bike ride or long brick or something that will help you feel really lousy so that you can see how your body reacts to being on the go for a long time. I also dont think the extra OWS experience will really be of much benefit (does one extra swim help?). I think it opens you to injury because most people push harder in a race, even if they say they won't. Plus it is expensive. So if you wanna do it, do it. I dont think it is necessary at all though. Good luck at B2B if you decide to do it. Its a wonderful race!