Sunning your lens for about 10-15 minutes to warm it up. Or perhaps send it to service center

its up to how long will u keep teh camera or how often u take it for shooting..
if u think ur house or room is humid and lots of dust (like me) u better get 1..
btw im live/work at genting...so a dry box is necessary to me

the main reason to get the drybox is to keep it from fungus..the cost servicing lens from fungus can go over the price of normal drybox..
still its up to u

if ur lens just kitlens, its not really a problem, just go out and shoot often, let it meet sunlight, even our skin will grow fungus if we stay indoor for 1 month.

drybox investment is depend on ur lens investment. dont dare ur house is made from drybox, if u own lots of goodie lens, get a drybox just for it.