I've gone through a few flash drives on my keyrings over the last few years.  The plastic ones tyopically break off after a few days.  I thought I had a winner when I first found an all metal flash drive, but the two halves separated after a few months.  I tried some of the micro drives, but found them fiddly to plug in when on my keyring.

Most recently I've tried the Kingston SE9 drives which looked like all of my flash-drive-related dreams had come true, but in 6 months we have had a 50% failure rate across 6 of the 16gb drives where when plugging one it it will get a little warm, and then stop responding permanently.  I've had warranty accepted on 3 drives and had them replaced, but I would much rather they didn't die in the first place.  It's embarrassing to have to go back to a client site to collect a data file for a second time.
http://www.kingston.com/en/usb/personal_business#dtse9h

I would love some suggestions as to a robust solution.

I have 8 keys on my keyring - all of them used weekly - plus a lanyard - plus a TILE.