I made a pot of the RG Ayocote Amarillos this morning, just to follow up on JoNorvelleWalker's experience. These beans did not have a best-by date on them (some of the non-Xoxoc RG beans do now), but I received them a couple of months ago. I made them with my basic-beans recipe, which is how I usually test varieties I haven't had before. It's not the same for every single type of bean, but anyway --
I soaked overnight in heavily salted water, which was then drained off. The beans took awhile to start puckering up, which I have not found to be unusual for the larger beans. In any case, they were squeezy-soft after the overnight soak, and had absorbed enough water that when I squeezed one, a small stream would spew out. Stands to reason, but I had never noticed anything like this in any other bean.
I cooked them in a clay bean pot with onion, green bell pepper, carrot, garlic, cilantro, celery, and a small amount of otherwise-unflavored ham hock stock. By small amount, I mean about a cup of pork stock, with the rest water.
I added bay leaf, black pepper, and a little more salt at the start of cooking. [I realize that this is against all kinds of rules and notions, but this is basically the way I make beans week in and week out. The seasonings change somewhat, but not the salt part. I am a serious salt person.]
Anyway, for the last few weeks I"ve been using the clay pot with no flame-tamer, right on the grate. So, kind of a high temperature simmer for the duration. The beans were edible if firm after about 2 hours of cooking. I then started reducing the liquid, and everything was tender and delicious by about 2 hours 45 minutes.
As I've noted, the only other Ayocote that I've cooked to date is the Negro, and it did not take this long, or even long enough to be notable. But, it is a significantly smaller bean. It looks like the Amarillos and the Morados are a lot bigger than the Negros and the Blancos.
So, the Amarillos took what is for me a long time to cook, but nothing along the lines of JoNorvelleWalker's experience. I suspect it was the soaking, for what that's worth.