All sealers are only as good as in how you care for the stone. If you leave acidic products on it, it will deteriorate. You will see this by a hazing of the sheen. Somewhere in the small print, this is on each product can. Many stones are sealed at the quarry, then again upon installation. But you must remember, no sealant, like car wax is for 15 years no matter what they say. The company I used to work for sold a 15 year sealer, but it was on there that it must comply with the manufactures specs. It is a loophole.
Take care of your stone by wiping spills shortly after they happen, use a cutting board (for the sharpness of your cutlery as well), and re-seal (wax on, wax off) at least twice yearly. It doesn't take much time, but well worth saving your investment.