I've found my ferro-rod on the side of the magnesium bar deteriorated almost 25% to a white dust in the car BOB once. Using an airtight container with silica gel pouch for all of them now (should do that for the spare bic lighters too).

Another time, when needed to deal with some ice, I've unpacked my car BOB just to realize that my Gerber folding shovel is almost useless, because I didn't check its condition in the unfolded position after a friend of mine has borrowed it once (like a year before the event).

With the PC mouse again. A while ago there were a trend in the ergonomic design with the silky rubber inserts on some of the high end models. After about 3 years in the drawer the rubber was like eaten by something (maybe mold, maybe natural decomposition, maybe an underneath glue diffusion). The surface became slimy and sticky, impossible to clean. I had to throw all 3 to the garbage.

Eugene. Okay. Maybe the fuse these days, right. But in the past I had this problem at least 4 times with the old Dell workstations and too smart students. In one case it was the chip on the keyboard, in other 3 - the motherboard was replaced (well, Dell said so). Perhaps, that happens on PS/2 mouse hot plug, not unplug. Or under some other specific circumstances (i.e. some buttons on the keyboard were depressed during connection). Better be safe than sorry.