Without knowing too much about AA, I can just add some details about the AY program.

Award miles do expire after 3 years, unless you hold platinum status and then there is no expiry at all.

Earning is based on distance flown, but with a tighter connection to revenue than AA has. Deep discount econ ticket may earn as little as 25% of distance flown while business ticket flown on AY earns 200%.

The low earnings on discounted fares are disliked by many, but it is the route taken by many airlines to minimize costs on the cheapest tickets. I personally prefer this system over the strict revenue based ones, as this is much easier to overview.