I've written before about how much better the subscription and exchange policies are at SF Opera than across the street at the Symphony. Yes, I understand that it's partly because they're handling a smaller inventory of programs and performances, but I maintain that SFS should be able to do a better job.
Now I've got another little marvel to add: because I only want to see five of next year's eight operas, I figured I would have to get a compose-your-own subscription. BUT SF Opera has an instant exchange policy for subscriptions: you get a subscription, and at the time of purchase, you can swap out 2 or 3 performances (depending on whether you have a half or full subscription) for something else. This extends to swapping opera A for opera B.
So, I can get five-opera sub and swap out Butterfly and Traviata for the operas I'd rather see. Hooray!