Originally Posted by
GUWonder
As you've noted, BA miles would be the best option for upgrading BA flights. And AA miles are good only for upgrading on AA flights.
[CX miles work too for upgrading, as CX miles seem the most versatile in terms of being used for upgrades on other OW carriers. That is, per
http://www.asiamiles.com/en/redeem/flights/charts/ , CX miles are useful for upgrading on CX, AA and BA.]
They're most flexible only if you can use them in time. AA and BA miles can be prevented from expiring via partner activity, so if you stay on top of it they never expire at no cost to you.
CX miles expire every three years. You can "renew" them (page 11 of their Asia Miles guide PDF), but you have to pay USD10 to renew every 2000 miles, so it could get costly if you take a long time to accumulate them for far-off usage.
For comparison, the last (and only so far) BA miles I
used (award or upgrade) was in late 2003, but I've been accumuatling slowly since then (hotel stays at hotels where BA earns flat 500 but US airlines earn much less for cheap one-night stays, Avis rentals, a bit of EC Dining here and there, and one or two Diners Club transfers but IIRC not since they went to only 50% bonus) and have 120k or so for future awards or upgrades. If this had been CX, I would have by now had to pay US$600 just to keep those around! Yikes!!!