For flooring, from what I have read, you are responsible for anything beyond normal wear and tear. Unfortunately, unless you know the carpet and its history, you may not be able to make a case for yourself. For example, if the carpet has an expected "life" of 10 years of normal wear, you move in when the carpet is 6 years old, when you move out 5 years later it needs to be replaced, that is replacing a 10 year carpet after 11 years, and totally normal. If you move out after 3 years and he is replacing a 10 year carpet after 9 years, you should only be charged the equivalent of the loss of that one year's worth of carpet (so a fraction of the replacement cost, not the entire cost). If you look up information with your local housing authorities or county and search for rental information you should be able to find everything you want to know, but it can be hard to get solid legal help with rentals.
If you took pictures when you moved in of the apartment condition, find those and keep them handy, or your checklist for the condition. When you leave and clean, take pictures and detailed notes of the condition you are leaving for your own reference to use to explain or make a case in case you get any charges you don't agree with.
My landlord recently re-rented one of his duplexes and was talking to me about when new tenants would move in but said he had some work over there repainting, replacing carpet, and putting in new linoleum, since it hadn't been done in quite a few years and had had a few tenants. He brought me some paint when I asked him (sheepishly) if he had any extra wall paint to touch-up with and pointed out that we had been living here for three years and there was going to be wear on the apartment (made me feel better).