Many forms of Granite are totally unabsorbent to water, grease, oil, solvents.. you name it ..
you can test yours by putting a tablespoon of water and covering it with a tupperware for 24 hours if the water still there at the end of that cycle you have permanent naturally sealed granite
If the water is gone and you have a dark wet spot, than yes it'll need sealing.
there are there are some Steelers out there that claim to be lifetime or permanent but that's only if you never clean the surface or subject them to UV or look at it cross-eyed if it indeed need sealing periodically try and do it at least once a year yours only neutral cleaners and don't let grease and oil and bacon fat and bong water sit on the counter for any period time