The always thoughtful Christopher Elliott has some valuable advice for airline miles club members: “assume nothing”.

What he means is, don’t assume you have enough miles for that free trip, and don’t assume your miles are sitting there waiting for you.

That’s because miles clubs change the rules all the time, and what you think you have, may no longer exist.

One thing you can do: check that little box that says something like, “Yes, I want to receive an endless chain of airline email telling me about my miles” – because, chances are, you could learn something, and avoid a nasty surprise when you go to use those miles.