1. Tears, holes, or a sagging panel
The obvious one. If bugs are getting into your lanai or you can see daylight through a rip, that panel is done. Small tears spread fast once the mesh is brittle, so it's cheaper to catch them early.
2. The screen feels brittle or crunchy
Give the screen a gentle push. New mesh flexes; old, sun-baked mesh feels stiff and crunches. Brittle screen will tear at the next strong storm — a sign the whole cage is nearing the end of its life.
3. Spline is popping out of the frame
The spline is the rubber cord that holds the screen in the frame's channel. When you see it working loose or lying on the deck, the screen tension is failing and panels will start to billow and pull away.
4. Storm damage after summer
After a rough storm season, walk your cage and look for blown-out panels, bent hardware, or debris tears. Insurance sometimes covers storm damage — take photos before anything is repaired.
5. Staining, mildew, or a "cloudy" look
Older screen traps mildew and hazes over, making your whole pool area look dingy. Fresh screen instantly brightens the space and improves the view.