Well this seems fun. I'll play!
--How often depends on the mood I'm in, what I'm doing, and if I'm using other forms of tobacco. Like I said in your other post, I may take a few pinches a week, or I may take a few pinches an hour.
--I don't own an actual snuff spoon, but I've put the spoon from a Czech pipe tool to use for that purpose. I don't really like using a spoon all that much - I find it unwieldy. Plus, if it is a scented snuff, warming the snuff in a pinch/boxcar/back-of-hand helps bring out the essential oils and really "opens" the snuff up. But, if you have any artisan snuffs (Old Mill, Rodinski, Sir Walter Scott, Open Source, etc), it's best to use a tool if only to scoop the snuff out onto your hand. Artisans aren't usually subject to the same anti-microbial treatments that the big companies use, so not introducing new wee nasties into the tin is a good idea: clean metal > grubby digits.
--I prefer the boxcar method for courser, moisture snuffs; for dryer, finer snuffs I usually go with the old fashioned pinch.
--I usually have a few tins open at once. If I open a tin and realize I'm not going to use it regularly in the near future, I close the tin as air-tight as possible and put it back in the "snuff fridge." Off the top of my head, I have a tin in my desk at work, two open tins at home that I snuff from, and probably half-a-dozen tins that have a few grams missing sitting in the storage. It's hard to say how often I'd go through 10g - if I'm snuffing a lot and only hitting the one snuff, less than two weeks. If I'm snuffing more casually and not really going to the same tin over and over it may be a few months.
--How quickly a snuff dries is based on packaging. A metal tin with a good screw top can hold moisture and aroma for a long time (years), even after opening it as long as you handle it properly. For me, that means closing it up tightly and putting it in the fridge. Others, like the Sam Gawith 10g Tap Boxes dry out very quickly - they often arrive dried out when I order them.
--Air and light are not nice to snuff. If you can keep your snuff stash sealed (if unopened) or closed as airtight as possible (once opened) and in their original containers or an opaque glass vial/jar, you'll be fine. All of my stuff goes into the fridge - it solves the air/sunlight problem, and also keeps them at a consistent temp and helps retard microbial development (for artisans).
--Whenever possible I prefer to use the original tin. In some cases, that's not practical. Sometimes I'll move a few grams of an artisan snuff to a metal snuff tin to carry around - that way I can pinch without worrying about causing problems. Some of the larger tins (25g toque, for example) are a little to unwieldy; others (Wilsons of Sharrow) can just be a pain in the neck to open - so I'll move them to small snuff tins to carry around. If you can, avoid the plasic "smash boxes" you can buy on Mr. Snuff - the scent will ghost that thing like a Lakeland pipe tobacco in a briar. Use metal or wood (that's been regularly waxed).
Why do I snuff? A lot of reasons...it's convenient, it's inexpensive, and the range of scents are amazing. It can bring natural tobacco goodness like a good VaPer pipe blend, or it can make good on all the promises aromatic pipe tobaccos have made and broken over the years.
