They are replaced when they go bad.
One week
What you meant to ask is how often should the timing belt be replaced! And the answer is every 90,000 miles for b2000 model.Ok
When they wear out.
about every 2 years
The Honeywell filter should be replaced every 8- 12 months or as needed.
Although there is no set on how often your brakes should be replaced, I would just pay attention to your car. When you notice something wrong, I would call your auto body shop.
every 6 months i think
Whenever they get REALLY yucky, or ripped apart.
Eyeglasses should be replaced typically every two years. Eyeglasses can break or if expiration is past then a new examination should be taken to get a new pair.
For allergy or general cleanliness health concerns the carpet should be replaced with a hard surface like wood or tile.
Hair entensions should not have to be replaced, but every five to eight weeks you should go back to the salon they were put in at and have them re-weaved.