Very late to this conversation but find it interesting.
What I haven't found is anything regarding the sustainability of VWC. But with the fact that you are generally using a weight which is most likely 20 lb. lighter than a bell that you own I would be interested in trying it out to see for myself. My next thought would be on the general strength program that one is using in conjunction with VWC as is recommended in the book.
I would liken it to a very good strength program that the trainee is using to increase strength, be it 3 or 4 days per week. Let's just use a 3x/week program that consists of bench, squats, and deadlifts. If you are really pushing this and then add say 2 days per week where you run at a 80-85% of your HR max then I would say that for 90% of folks that is not sustainable. Eventually you'll see the training "hangover" that Brett mentioned. Next you'll see the amount of weight you are using on your lifting days start to plateau or even decrease. Now I'm talking about a strength program where you are using 90% max on at least one day per week and never less than 75%.
Of course this is all considering that everything else is in place. If you've got a big work load, family commitments, or other stressors then it could be worse. Then again, if everything is in place and you are young and eating correctly it may take a much longer time for it to catch up to you. Just my opinion.
Everyone is different and it will be interesting to me to see what happens here. Personally, I would really temper my general strength training during a VWC cycle. I would expect to lose a little strength. But if you are training to increase VO2 max then nothing is hurt. It's tough for the "average" cat to have more than a couple goals in place and not see some other area of his training decline. It just happens. That's why I think one really has to figure out what is the goal.
As far as comparing this to Maffetone's ideas and A+A they are apples and oranges. Maffetone's 180-age as a training heart rate is to keep you in a zone that for all intensive purposes should not cause overtraining and will teach your body to use fat as fuel. The same when training in an A+A style. You are giving yourself time to rest between sets, keeping the HR lower, and therefore using a heavier weight. The idea being that you will get stronger with the heavier snatches, you will increase your endurance and work capacity, and by adding some LSD aerobics at a MAF HR increase your aerobic capacity with the benefit of heart and lung health.
Generally the A+A style "should" be a more sustainable method that would not cause injury or overtraining.
And generally by training in a HIIT method such as VWC you "might" see some periods of "training hangover" such as Brett talks about.
@Rif has the most experience so I would be interested in his input on this. But did you notice that Rif was training VWC "once" per week. I believe this was a very good decision made by someone with loads of training experience.
Another remark is using the VWC to increase snatch test results. I do know there is a TSC participant who has good luck training snatch cadence to increase his numbers. So given a 5 minute test that may have some use. For the SSST I think it just comes down to more of a mental thing. Just my opinion and that and a dollar will get you coffee anywhere but Starbucks.