Do as you want but unless you can 100% guarantee the exact tank YOU analyzed and didn't let it out of your site (including when transporting with other peoples) you will want to check right before the dive. I like the comment above about your buddy knowing what mix you are running should they have to breathe off your tank. If you were going to omit one of the two analyzing sessions it would be the one at the shop you got the fill. That way you are still checking right before or at your dive and know exactly what's up. Obviously being a bit facetious there but you get my point.