There are advantages and disadvantages to retracting a screen. If you are going to leave it un-retracted, it is better to have a fixed screen, as those can be stretched to be more perfectly flat and give you a better picture. For a truly dedicated home theater room, I think a fixed screen is the best way to go.
The advantages to retracting are that it can help protect the screen from damage when not in use (though one can use curtains that close in front of it if it is a fixed screen), and also one can put the screen in a place where one does not always want a screen if it is retractable. Thus, a retractable screen can be more appropriate for a multipurpose room (as opposed to a dedicated home theater).
Of course, retracting and un-retracting, your mechanism can eventually wear it out. But if it is of decent quality, I would not worry too much about that.