I have just booked a trip to Europe on which the transatlantic segments are on BA.

I am AA basic member and fly less than 5000 miles/year on AA and do not expect that to change.

Instead of signing up for BA's program just for miles on transatlantic segments, I would like to sign up for one program, where I can get miles on AA and BA transatlantic as well as for AA USA domestic.

After doing "research" I am tempted to sign up for Cathay Pacific as the miles do not expire.

Am I doing the right thing?

Thanks