The general rule is that if the tenant has damaged something that does not normally wear out or has substantially shortened the life of something that does wear out, the tenant may be charged the pro-rated cost of the item, taking into account how old the item was, how long it might have lasted otherwise and the cost of replacement.
So when determining how much a Landlord can deduct from a tenant's deposit for actual damage by the tenant (not wear and tear) it's important to remember that the original condition and age of the item at commencement of the lease agreement need to be taken into account, and therefore cost of depreciation of the item due to normal wear. i.e. if at the end of a tenancy it's found that there is a tear in a carpet, the tenant can't be liable for cost of a brand new carpet - depreciation has to be factored in.
Paint fades, doors and walls get scuffed with use, and everything wears or breaks over time, even with a tenant who really cares for the property, and one can't hold a tenant liable for this.
On the subject of paint - if a tenant drives nails into the walls (only with landlord's permission in our lease agreement) they would have to make good when they leave by removing nails and painting - and unfortunately, unless you have exactly the same tin that was used originally, it's unlikely the paint dye lot is not going to be same in a new tin, therefore the entire wall (or room) will have to be painted. If the tenant merely painted over the filled holes and the paint didn't match, this could be constituted as damages, recoverable by the landlord.