The waves develop due to environmental conditions, not from raising and lowering it. I had a screen I kept down for 2 years - it got waves in it.
Understand please, that IMO motorized screens without tensioning is one of the most wasteful things people can buy. You can purchase a manual pull down screen for hundreds of dollars less that will last just as long. Yet, people spend hundreds of dollars just so they don't have to get up off the couch and reach up to pull the screen down.
If the hundreds of dollars was for a screen that outperformed the manual screen, or would last far longer, then it would make sense, but non-tensioned motorized screens do not last longer, and are simply a complete waste of your cash.
Tensioned screens, on the other hand, should look just as good 10 years from now as the day you bought it.
Of course, the best way to go is with a permanently mounted, fixed on wall screen whenever possible.