A tenant is obligated to maintain an apartment in the condition it was found in and is usually liable for any damage she causes to the property. Wear and tear of the property is to be expected, and it is illegal for a tenant to be charged for repairs to the property which fall under the wear and tear exception, even if she has lived in the apartment for over 10 years.
Normal Wear and Tear
It is illegal for your landlord to use you security deposit to pay for repairs resulting from normal wear and tear to the apartment or to charge you separately for repairs, regardless of how long you have lived there. Normal wear and tear is defined as the aging or degrading of such materials as wall paint and carpet that would occur even if you didn't rent the property. In other words, it's not your fault that paint fades or carpet wears down over time -- it would've happened anyway.
Damage to the Property
It is perfectly legal for your landlord to charge you for repairs to the property that fall outside normal wear and tear. Acceptable repair charges can include cigarette burns in the carpet, carpet staining due to pets in the apartment or damage to the paint caused by furniture or objects rubbing against the walls. Accidental damage to your apartment's carpet and paint are more likely to occur the longer you live there. It's important to make your landlord aware of damage to the apartment as soon as possible so appropriate repairs can be made.
As a tenant you are obligated to keep your apartment clean and relatively tidy while you are living in your rental property. When you are moving out, you are also obligated to return the apartment to as close to the state it was when you first moved in. This means you may have to scrub the floors, wipe the walls and have the carpets professionally cleaned. If you elect not to clean the carpets, your landlord can change you to clean them by deducting money from your security deposit.
Tenant Protection Methods
To protect yourself from repair charges for damages that are not your fault, it's important to walk through the apartment with your landlord before you rent so you both can agree on the condition of the property. Create a checklist while doing this so you have a hard copy of the state of the apartment to refer to later. You may also want to repeat this process at every lease renewal so the landlord can review the property personally. This way, when you move out you and the landlord already have an understanding of the condition of the property and if he tries to charge you for repairs that are not your fault, simply refer to your apartment checklist.