I doubt that you could charge a tenant for damage to an eight year old carpet. The danger would be if the tenant challenged the deduction and the court reduced the deducted amount. That would mean that the tenant would be the prevailing party and entitled to court cost, attorney fees and potential damages. That's a very high risk for a few dollars.
The IRS puts the depreciated value of carpet as five year property. What that means is the the IRS has found that carpet last between 5 to 9 years on average. Higher quality carpet toward the nine year mark and lesser quality carpet the lower number of years. Most courts go by these standards. Of course a landlord could argue that their higher quality carpet should have last longer, but that's a high hurtle to achieve. Most landlords use either 5-7-10 year depreciation standards as a guide for charging a tenant for damages above normal wear and tear as that is what most courts accept. It could be argued by your tenant that the carpet has seen it full useful life and has no remaining value to the landlord. Remember, it will be the landlord who has to prove the value of the carpet.
So if it cost you $1000 to replace carpeting and the old carpet had a life span of tens years. You are only talking about $200 and not really worth the risk of losing in court and paying thousands in court cost and attorney fees, plus paying for your own lawyer too.