Realcent.org

While cooking up some of our preps, [store what you eat eat what you store]
My wife complained that the beans weren't getting soft enough.
Sure enough I saw on other forums people with the same complaint.
One guy even said "you might as well just try cooking the rocks".
any ideas on this?

Pintos get hard when they're old. Storing them in nitrogen or CO2 could help. Also avoid adding any sort of acid until they're soft.

For the beans you already have, try an overnight soak and/or pressure cooker. One thing I haven't tried is doing a soak with a little baking soda, but I'd love to hear if it works.

I don't understand, really. You start with an overnight room temperature soak then cook them with lots of water. Hard to cook them too much. Keep adding water and heat until they get where you want them. A pressure cooker speeds things up but isn't necessary. People that are used to microwaves may not appreciate that this is a long process - it doesn't get done in minutes or even an hour. Multiple hours required.

Pinto Beans are something that we cook regularly.
My wife has been making them for many years,
cooking these twice as long still keeps a lot more "tooth" in them.
I may have to try storing in CO2.
good thing I only have a couple of years worth stored.

I will buy another pressure cooker.
My canning pressure cooker [a 34 quart All American], states never to cook beans in it.
Any ideas on why?

Dunno for sure from personal knowledge but I suspected it was this, and then one of the first search results seems to confirm it. Emphasis mine.

Pressure cooking beans is fast and easy, but you MUST use oil when doing so. It keeps the beans from foaming up as well as keeping the skins from popping off and clogging up the vent tube. Remember not to fill cooker over 2/3 full.

You need to soak pintos until they all get larger and none of them have wrinkled skin. Soaking them some place warm helps, too. I used to leave them out on my "porch" until it got cold and the beans took a week to soak. Just keep changing the water as soon as you see some foam on the surface, or more often. The fresh beans are paler on the light parts, and taste better.