I think it depends on your personal travel habits. Signing up for a loyalty program might start to change the way you want to travel. If you're the type of traveler who always shops around for the cheapest airfare, then you probably won't accumulate enough miles in any one plan for it to be worthwhile given the short expiration date for miles these days. If you're wiling to stick with one airline, then by all means, go for it since you have nothing to lose.