Sealing your granite is one of the many things you just need to put up with if you want to own this type of countertop. When you think about it, it really should come as no surprise that granite needs to be sealed. It is like any other organic material. Wood has its grain, stone has its porosity.
Types of Granite Sealers to BuyFrankly, I have not learned about any clear preference for granite stone sealer products. Black Diamond Nex-Gen Granite Stone Sealer is a type of product that you see on store shelves quite often, and the price is reasonable.
Keep in mind, the price is really not much of an issue as this stuff goes a long ways. Just a few squirts are usually enough to fully coat an average sized bathroom counter. Yes, you will be doing two or three coats on the counter, but you will find that each subsequent coat spreads even a little bit further.
Really, granite stones sealer is nothing to stress about. If you don't get it on right away, it's not like your granite is permanently damaged for life. But certainly seal before too water gets on your counters, and especially before any kind of stains occur (which would be permanent!)