Over the years I've joined QP a couple of times, and it made perfect sense to me. My travel varies based on work and a couple of times I've ended up losing all my status. Then when I get a new travel gig I join QP as I know it may take me 6 months of solid Econ flying to get back to gold. Then a few years later when my travel drops off again and I eventually lose my status again, my QP cuts in for however much time I have remaining on it.
I have to take a hit again on the joining fee each time I rejoin, but if I'm not going to be travelling for several years at a time, that's still the best way for me to play it.