We recommend watering proofing Sunbrella covers every 2-3 years. Sunbrella comes waterproofed and will need to be treated again if it gets washed.
The key to a long lasting cover is to keep it clean. With high end materials such as Sunbrella, Stamoid and Aqualon, your cover should last between 7-10 years. If good care is kept, the cover can stay with you for up to 20 years. Around 20-25 years, however, the fibers tend to break down and the material will not keep out as much water as it once did.
303 Fabric Guard is a great product to use for waterproofing and cleaning canvas. Some cleaning products for vinyl cushions we recommend are 303 Multi Surface Cleaner and Sea Foam (only for harsh stains, we don’t recommend over use of Sea Foam for cushions that sit in the sun).