I understand the "normal wear and tear" policy in terms of security deposit. My question is, if I've lived in my apt. for 5 years, the amount of "normal wear and tear" let's say, of my carpet, would be [more likely], more so than someone who has only lived there for a year. In other words, does length of tenancy play some role in determining "wear and tear"?

Yes it does. Why is this an issue?

Because I was told by the apt manager and the landlord herself, that she deducts a "cleaning fee" automatically from the security deposit, I told her it was illegal for her to do that - UNLESS, there is excessive damage, beyond normal wear and tear. She said that "everyone does it -ask anyone". If it is not stated in the rental agreement that there will be an ADDITIONAL charge for a cleaning fee when you vacate the apartment, it is not her right to do so. Correct?

ANY question on law needs to include your general locale as laws vary by area.

ANY question on law needs to include your general locale as laws vary by area.

It is Los Angeles, CA

Actually its not illegal, but it can be questionable.

California Civil Code Section 1950.5 only permits a landlord to use a tenant's security deposit to pay for the costs of: (1) unpaid rent; (2) cleaning the rental unit after you vacate (but only to what it was before you moved in);
California Law Regarding Rental Security Deposits (http://www.yourlegalcorner.com/articles.asp?id=102&cat=land)

So, normal wear and tear doesn't come into it. If you can prove you restored the unit to its move in condition, you can can protest the fee.