Yeah, with the various multi-airline alliances these days, that SHOULD be true. But the problem I've run into is that the airlines are VERY reluctant to make free seats available to their partner airlines. For instance, I concentrated my Star Alliance mileage credits on US. Repeatedly, though, when I needed a ff ticket on UA, UA's website showed award availability when US couldn't get me a UA seat. So now I also maintain a UA ff account (funded largely by the absurd generosity of the credit card sign-up offers).

Obviously, the airlines can legally adopt any expiration day they want (provided they give adequate notice). But these are LOYALTY programs, and I would think that a signal that the most frequent flyers (flyertalkers) are unhappy with the changes might curtail this unfortunate new trend.