i guess this pertains to any screen. i notice all screens are fiberglass mesh and seem looose. in the future, could i have the mesh removed and use a more rigid aluminum screen? would that work in the screen frame?
If the screens begins to sag, all you need to do is buy a screening tool for $2.99 and tighten them up. Sunrise does offer a lifetime warranty on their screens but sagging isn't considered a defect in workmanship. You could also replace the fiberglass with aluminum screens.
Stick with the fiberglass mesh and just re-tighten them up.
Aluminum screening material will oxidize over time and leave that gray residue on the frame and glass.