I have no idea how many I've bought over the years, some have quit working, some get misplaced and left in bags and some I have no idea. I keep a couple in my truck, one in my turkey vest, one in my satchel, one in my deer backpack, in tackle bags and fish cleaning bags. During deer and turkey season, I usually carry 2 in case one malfunctions.
One trick to lighting is to turn it on and do not click it for 3-4 seconds to allow the butane to gather a bid in the housing and to light it straight up and down and not flat. I also use the pads until the quit working and not a set amount of times. I've ended up with a lot of pads and short of butane.
My biggest gripe is when they did away with the holster that had the strap with belt snap, it was much better than the ones with the clip on feature. you could strap it on anything where I find the clip aggravating.
Someone mentioned DEET and it works good, but I've seen it take the finish off of bows and it has caused my hands to swell and my lips to swell after sweating and running down my face.
We used the lanterns at the pool for a few years until a couple of buddies of mine started a mosquito spraying company and now they keep my backyard sprayed for me and I have no mosquito issues at home anymore. One of the guys is also a member of my hunting club and sprays around the clubhouse during deer season, so thermacells aren't needed in camp anymore where we used to run a couple every evening during the fall hunting.