The snuffs that last longer for me tend to be the dry ones, I have never really got on with them which is why I not only use them less often than my moist snuffs but (as betonente has said) I take smaller pinches.
My Fribourg & Treyer snuff is my overall favourite so they last even longer as I don't use them that often (save them for a treat after a hard day working)
depends on which brand. I generally use dry snuff and so I go through a lot more of it than moist snuff. But when you talk about a tall tin of F&T or a tall tin of American snuff, obviously those will last a while longer. But if we are talking about equal size containers with equal amount of snuff, I would have to say the moist snuff would last longer just because I use it less frequently, and considering most of your moist snuffs contain menthol which I'm not a huge fan of. With obvious exceptions to the few more moist snuffs I really like. Something like Sam Gawith Black Coffee, I can go through a container every 2 days if I wanted to and didn't use anything else. But having a large selection, everything last a while just because I don't stick with just one snuff. A couple different ones each day.
I'am taking this question in a diffrent way. Which lasts longer in the nose. For me moist snuffs seem to last longer but take longer to give me a lift. Not much of a total diffrence but a small one.
I think it more depends on the flavour for that. I find most of the F&T snuffs (usually very moist) last ages but the longest I have tried seems to be Molens Prins Regent and Pompadour (great snuffs BTW), I can often still smell them hours later.
If you are talking about nicotine I don't know as I rarely feel it and usually don't go without long enough to get any sort of craving.