Actually, I think you're right, jamflyer. I didn't realize that bonus miles and credit-card miles also count toward AA lifetime status - so I would probably reach Lifetime Gold in 5 years. If I understand correctly, 1MM with UA confers a better Lifetime status (Premier Executive), but only *base miles flown* count in that program, so it's more like attaining 2MM on AA.

The main drawbacks I see with staying with AA vs. US/CO seem to be:

1) Weak alliance and international presence - so no non-stop flights to AMS and TXK;
2) No Economy Plus seats - though we usually get exit seats, so this probably isn't a big deal;
3) No Premium Service trans-continental flights;
4) Older planes.

But (1) and (4) are the only serious drawbacks, so it looks like the benefits of staying with AA may outweigh the drawbacks.

If I've missed any important elements in this consideration, please let me know.

Thanks!