They do eventually wear out if you are cutting through your material on them. I’m on my third mat in something over five years. I cut several hundreds of jobs on paper a year. I am not aware of anyone else here wearing out even one mat yet.
If you are careful to adjust your settings so that you just cut through the material (using this method, perhaps), you will minimize damage to the Seklema mat.
If you are just holding leather patches down while you engrave them, I would not expect you to be damaging the Seklema mat much at all.
Ash accumulation will make it less tacky but, you can clean that off with isopropyl alcohol and paper towels periodically, as needed.
The mats are double-sided. So, you get two sides to wear out per mat.
As @ekla suggests, a piece of MDF coated with the Odif 505 Temporary Spray Adhesive will also work well for some stuff. The cost of a can is probably worth a try if you are hesitant on the Seklema mat.