Two 140.6 races 3 weeks apart.

Just out of curiosity why are you doing 2 races so close together? You might also want to ask your question over on Slowtwitch. I know a lot of people have raced Kona and another IM either right before or afterwards. It can be done. I would imagine that you would have to determine which race was your "A' race of the two. Good luck!

I'm doing Ironman Canada and Ironman Mont-Tremblant this year... three weeks apart.  I was originally going to do IMCdA instead of IMC but I have been dealing with some medical issues that has kept me from training so I need the extra four weeks on the calendar that IMC offers.

I asked some folks who have done IM's 3-4 weeks apart and the conventional wisdom was:

- Choose one as your A race and stick to that mindset.

- If the first race is the A race then go all out as you normally would and then do everything in your power to rest and recover as best you can.  Get a nice message the day after the race, stretch, maybe get in the pool later that week and do some easy biking the following weekend.  Basically resting up.  Week two would be like a normal taper the week before a race.  Just be mindful of the running so you don't hurt yourself.  Week three is race week.

- If the second race is the A race: Do a one week taper before the first IM.  Race the swim and bike as you normally would but don't go your 100% on the run.  Go 90-95% on the run.  Same advice as above, massage, rest and recover for a couple of days and then do some easy S/B/R the rest of the week (max bike of 2.5 hours, max run 75-90 minutes).  Then go into a normal two week taper to the second IM.  Think of the first IM as a huge training day for the second.

- IMMT is my A Race.

Absolutely.  I'll be doing IMC as my B Race/Training Day and IMMT as my A Race.

I kind of did that last year.  Did IMC as a huge training day before IMFL but there was 9-10 weeks between races and not 3 weeks.

The 2014 races will be IM # 6 & 7 but four in a 51 week period (IMC, IMFL, IMC, IMMT).

Did one in 2010, 2011, 2012.  Two in 2013 and two in 2014.

I did IM Canada (Penticton) and IM WI 2 weeks apart back in 2010.  My approach was to try to KQ at Canada and then do minimal training for the 2 weeks after to recover and simply see what happens at WI with no time goals in mind.  I won't get into why I attempted this, but I won't try it again.  I had some GI issues in both races but I was able to overcome it somewhat at Canada by walking a fair bit on the run to let my stomach recover and ended up with a 10:57.  I didn't have the same luck at WI and stomach shutdown forced me to walk a death march for a majority of the run (14:16 finish).  I've since figured out the nutrition issues.  However, the one thing I remember most during the second race was the lingering fatigue from the previous race.  I felt it in my legs pretty early into the bike.  You have an extra week but you likely will still feel the first race a fair bit.  Good luck.

Haven't done it myself but I have a friend that (in 2012) did IMMT one weekend and then flew to Penticton and did IMC the following weekend.  His finish time for the two races were within about 5 mins of each other.

Try to finish the first one at a pace that is psychologically painfully slow.  But not physically.