Aqua Mix Sealers Choice Gold
The price is a bit more reasonable than some of the other options on this list and becomes more reasonable with the anticipated 15 year lifespan. It absorbs well and penetrates to a moderate depth, so expect to apply two coats as directed and possibly a third if the stone is very thirsty. Happily, the odor of this sealer is very reasonable and light thanks to the water based formula. I have not been around long enough to see if this will indeed last for 15 years, but it shows no signs of quitting after three years.