1: If blinds, screens,screen doors, curtains or other window coverings we provide need repair/replacement, and we determine that the cause was not due to a defective product or installation, we will charge you a PRORATED CHARGE using the expected life (# of years) of as below.

2: You will NOT be charged the cost of cleaning or/and lubricating window tracks and rollers

Blinds: 7
Doors: 20
Curtains: 7 

Screens: 15 (Exclude any damage that repairperson says was caused by the sun) SOURCE: LINK

Screen doors: 30 . You will not be charged if the door needed to be replaced due to the problem with the lock not being installed correctly originally 
Window Glass: 7 (Broken from outside for multi unit properties,tenant not responsible)
Windows: Aluminum 15 
Windows: Wooden 25
Windows: Double Pane 15 
Windows: Skylights 10 
Windows: Louvre 10
Windows: Vinyl/Fiberglass 20