Currently there is that extremely thin, hard, cheap landlord carpeting (and also an area with cheap thin stick on hard tile squares). 

Since this situation was so egregious (IMO), I would either boot them out now, or at least have a serious talk, real serious....If you're going to let them stay I would just get a really deep cleaning done, maybe a couple, and then replace carpet after they're gone.

Looking to remove knee wall and carpet from staircase and add stained treads, handrail, balusters, etc. 

My lease requires professional carpet cleaning, which would cost more than $500 for a home of that size.Yes, it's reasonable to reduce the cost because she was such a long-term tenant.

Example of what a tenant might say - this 2x2' stain on 2 year old carpet was already there when I moved in.  

To set the scene: A cost seg study breaks your property into two important categories:1250 "real" property aka the building, foundation and other long life assets.1245 property aka anything that can be accelerated such as 5, 7, or 15 year property like carpets, cabinets, or other site improvements.

I have added new electric service, all new plumbing, an additional bathroom, remodeled Kitchen all the way down to the studs, new carpet on the second floor, and new LVP on the first floor.

Not gonna put it over the carpet. 

doesn't make sense to treat the house then throw all the stuff away, and replacing the carpet and repainting the entire house2.

Thinking of changing landlord carpeting to some type of lvp before renting it out.