Miles don't create more value sitting around and typically devalue over time (not that the greenback isn't in the same boat, but the greenback has a bit more flexibility). If/when I have more miles than I have an immediate plan/goal for then I usually am happy to use them for $0.01+, although I've dipped below 1 cent a few times depending on the # of miles I have relative to what I might use anytime in the future.

In summary, this really depends on what's best for your travel & finances, but if you don't have a plan to use miles/points anytime soon and have a sufficient buffer for unplanned trips, then burn vs stockpile when it comes to miles/points. (my 2 cents)