I think I went the first 5 or 6 years without ever losing a hammer, and now I couldn't tell you how many I have replaced. I usually lose the occassional tool more than the frequent one because I forget that I used it or do not think to check for it in my bag when I cleanup.
Here's an add-on question if it hasn't been adressed already, how many of the "lost" tools do you find right after buying a replacement. Bought a new pair or wire strippers a few weeks ago and found my other pair the next day at our shop. Talking to my brother on the phone, looked down, there they were. :roll: