I havent heard of anyone sawing through their guide rail, but I have heard of people sawing through the aluminum table profile (especially on the far side).
As a safety precaution, place the limit stop (part #491 582, normally used for plunge cutting) near the end of your MFT's guide rail. Align the limit stop at the seam where the MDF meets the aluminim.
Keeping the limit stop locked there should prevent you from ever sawing through the aluminim table profile, and there is nothing new to purchase (you should have received on with your saw).
Bill