The posts above cover most of the answers. There are so many variables involved—how much propylene glycol is or isn't in the blend, the seal of the tin prior to transferring to another container, tobacco cut, relative humidity in the area, etc.
What I find interesting, being both a cigar and pipe smoker, is that with cigars, there's a greater focus on maintaining a relatively constant humidity (often between 65 and 70 percent, depending on how you prefer your smoke) and temperature (under 70 degrees Fahrenheit to prevent tobacco beetle eggs from hatching), and that circulation of fresh air is encouraged in the equation to keep the sticks from getting musty. It seems with pipe tobacco storage, pipe smokers are content to keep things in a sealed jar, with no consideration for getting fresh air into the mix (perhaps, more out of a concern of preserving existing moisture or creating aging conditions).
I use humidification beads in at least one of my pipe tobacco jars and most of my cigar humidors, although I'm considering switching back to green florist foam for one of the humidors, if only because it's easier to get a quick visual on the moisture level when refilling with distilled water.