That's funny

For us, we tend to save them with some specific goals in mind, though out planning tends to go out a year or two in advance.

One factor is if you're earning/burning as a single person, a couple, or family with kids. With 2 others in the household to get places, braces to pay for, college expenses coming up, etc we have much more need to cash in miles if we're going to go on some cool family vacations.

If I were by myself, I bet I'd have more miles than I could use at the moment. And more than likely I'd be using the miles for upgrades or lounge membership.

I'd say, think about places you'd like to go, make plans for when & where and then get some good use out of the miles. All in all it's a balancing act and highly individual. But as others noted, devaluation hits eventually so use 'em while you got 'em