Kind of hard to answer without knowing what pipes you are smoking...I have pipes that last 15 minutes and pipes that will go for 90+ mins. You need to factor in tobacco cut as well. A MM legend full of Carter Hall will probably last me around 20 minutes where as a folded flake of FVF in the same pipe will go 45 mins. A lot of factors.
Smoke density is a good factor. If it goes out pretty much instantly after lighting it, then you are probably to the dottle. Also taste plays a big part of it. If it taste terrible and like ash, you are done. It is a lot like the nub of a cigar...when it becomes harsh and bitter, time to call it quits.
Another "depends" answer. Samuel Gawith flakes can go about 2 months in a tin and be fine. A fine Burley can dry out on you in as little as 3 weeks. A goopy aro will last eternity (but will lose flavor). My general rule of thumb is get it into a jar within a month.
I don't worry about this stuff. I buy jar. I put tobacco in jar. Me smoke tobacco. :p
I would rather have a lot of 8oz canning jars full than bigger ones half full though myself.
I don't smoke indoors, unless you count the shop and garage indoors. I think pipe smoke sticks around and stinks up stuff just as much as cigar smoke does. The main difference is there is a lot less smoke produced I would say when you puff a pipe, and in general, pipe tobacco isn't as pungent as cigar smoke is. Unless you're smoking latakia. That stuff will stink up a room.
I love coffee with Burley and Va. Black/green tea goes well with all pipe tobacco in my opinion. I like peppermint tea with latakia, that is fun to me. Water is always good with pipe tobacco. I drink a lot of beer with my pipes too...but I have been told my pairings are awful so I won't share them...I like bold flavors and people complain that their taste buds aren't manly enough to handle all the flavor awesomeness that mine can. :p
Don't use craft cleaners for your pipe. They are for crafts and not absorbent like "true" pipe cleaners are.
Nice Questions!