If your contents insurance has a new-for-old policy, if you make a valid claim for a stolen or damaged item, the insurer would pay for a like-for-like, new replacement or repair it as new. So wear and tear or how it might have reduced in value over time won’t be taken into account. The exception may be for belongings that wear out fast, such as bedlinen.
If you have indemnity cover, which is much less common, your insurer pays for a replacement that reflects what the item is currently worth, bearing in mind its age and wear and tear. Your premiums are likely to be lower, but make sure you would be comfortable with only getting the value of the older item.