Sealing slate backsplash
I just had my kitchen backsplash tiled with 1 inch mosaic slate. I also paid to have it sealed and bought some sealer/enhancer. The installation guy did not seal the tile before grouting and told me it takes about 10 days for the grout to properly cure then he will come back and apply 2 coats of the sealer right off the bat and if I decide I'd like more coats he would come back to do it again.
So I've read a little on the subject but can't find a consensus on how many coats should be sufficient. I've seen 2 coats and a lot of 3 coat minimums but they are often for bathrooms so I think for my kitchen it might be overkill since it won't likely even be wiped down but every week maybe. I have also read that slate is very pourous though so that may be more of the issue.
So my questions are: How many coats should I insist as a minimum, Should he have sealed at all before grouting and why, Can you apply 2 coats right away without waiting for the first coat to set (bottle says 30 min), and How long can I expect this sealer to hold up before another application given this is for a kitchen?