I've come to realize that wings on the DF have a limited lifespan, even if you don't crash them...to explain.
Over time it became obvious that the plastic in the wings stretches from use, causing slack...and this negatively impacts their ability to produce thrust and thus, lift. Very much so in fact. I
I'm not sure how many flights you can get on a set of wings, personally I do about 10 flights in a day, outdoors. It should also be noted that flying over hot asphalt or concrete is a bad idea since, if the wings touch the surface the plastic could easily deform.
Back in the old days we used to use a type of glorified Hair Dryer to get monokote to shrink and stick to wings...I have not tried it but perhaps a gentle application of hot blow dryer could rejuvenate DF wings? If somebody tries this, and it works, I have no doubt this would be a great boon to those who fly and love the DF.