"Ordinary wear and tear" is used to describe amount of allowable deterioration to property without tenant being financial responsible.There is no exact amount of time specified by law that each item in a property should last before being considered worn out.
Tenants should not be responsible for costs that are considered normal maintenance. What's normal?
Landlords that install cheap carpeting must expect that carpet to show wear sooner than a better quality carpet. That wear is not fault of tenant.
If your property is rented to a family of six it will show more wear then if is occupied by a couple.
What is normal and ordinary wear and tear defies exact definition... even for most conscientious owner.
To avoid as much controversy as possible every landlord should have a new tenant inspect property and fill out a property inspection sheet.