The vent guards on my work truck are the stick on 3m deals and they have been through plenty of drive through car wash time with no sign of coming off.
Properly applied these items will not fall off and you should have no concerns. Look at all the vehicles with moldings running down the sides of them, those don't just fall off without a ton of effort. Granted they are a bit smoother and streamline/tight to the body than some of these scoops.
You just have to be sure to prep properly. Be anal and clean up the area before install. Depending on your location, make sure the surfaces are relatively warm and if possible let the car sit in the sun for a few hours after install to assure good adherence. My 1/4 scoops and such routinely see 130-140 on the speedo and they show no sign of falling off.