I have a bunch of these things. I use them mostly for moisture protection for firearms, since I live in very humid South Georgia. I have found that these 40 gram units work very well. I check the indicators on them frequently, and find that in summer they will need "recharging" about every two months, in winter only about every four months.  This refers to items kept inside an air conditioned house. The recharge is really just drying the silica gel, done in an oven set at 300 degrees for 2-3 hours.  No odor, so your wife won't get mad..I stick mine on a cookie sheet and let them bake while I do other chores. Good product, recommended..beware of some on the market that LOOK almost the same as these, but contain less gel, or crummy gel.  The knock-offs are usually much lower-priced than these, but are a total rip-off.