It really depends on the age and condition of the carpet. Seven years is about average, but good carpets can last 15.
If you want to get your cleaning deposit back, clean everything thoroughly, including the carpet, and make sure the landlord knows so he or she can inspect it.
A landlord can charge for excessive wear and tear on carpet only if it's unreasonable wear and tear. After five years, according to national standards, a carpet is deemed to be completely worn, and such wear is considered reasonable. So in answer to your question, the newer the carpet, the more the landlord can charge if the carpet is damaged, if it is damaged outside the reasonable wear-and-tear limits.
Depends on how the lease is written: normally the tenant is responsible for painting interior.
The landlord can never charge for normal wear and tear. If the carpet is unfit for further use after 4 years, that's abuse, not normal wear and tear. If, however they just show their age, you cannot be charged, your duty is to have it cleaned, that's it. A landlord is only obliged to replace carpet that is no longer fit for use and that is not tied to any number of years, it is all about the condition.
If there is a provision on the lease which requires that your carpet be cleaned six months prior to the expiration of the lease, then the landlord has the right to enforce those provisions. Additionally, if the carpet is damaged or dirty because of obvious abuse by the tenant and not the cause of normal wear and tear on the carpet, the landlord has the right to demand that the carpet be cleaned. However, if the carpet was not brand-new, then whatever dirt or damage occurred to it is measured according to wear and tear by the age of the carpet. Carpeting of five years of age or older is usually deemed to have reached its maximum age, for which the landlord has no claim. Finally, the landlord may not keep your entire security deposit simply because you didn't clean the carpet: he can only deduct the cost of cleaning the carpet from the security deposit. I doubt that your landlord can evict you simply because your carpet is dirty. If you have only been in your apartment for six months and your landlord evicts you because the carpet is dirty, then I would take pictures and present them to court to fight your landlord.
You and only you !
Probably only if the carpets are old (seven years is average). Your allergies probably isn't the landlord's fault. You might want to move to a place with hardwood floors, and he might be wise to let you go.
No, there is no requirements to replace carpet, ever, as long as it doesn't pose a health issue.
Only if required for health or safety reasons, or if they want to make the tenant's stay more pleasant.
no. not as long as you live in the us.
This all depends on the terms of your lease.
30 days in writing if by notice you mean eviction