Easy. Just replace it when it needs it. If it's cracked, chips are missing, etc.
Takes a 1/2" socket drive in the idler arm. Take the pressure off and take the belt off a pulley and just take it out. The only this is you have to undo the top end of the upper radiator hose. When the coolant isn't hot (there's no pressure and the coolant has had time to settle down in the block and such) undo the clamp, move the hose outta the way, slip the belt over it, and there ya go. Reverse for new belt.
You can always get a dual alternator upper radiator hose. They go AROUND the belt and fit into that semi circle cut out of the alternator bracket. Why Ford made it different, idk.