I keep a significant portion of my bitcoins on an encrypted ironkey usb drive stored in a security deposit box and stored in a zip lock bag (in case of vault flooding, which was an issue in Manhattan after hurricane Sandy, although the ironkeys are very well contructed and would probably work after a year or more underwater). The ironkey uses hardware-based encryption and automatically erases and disables the drive after 10 wrong password attempts, so brute force isn't an option. The file on the drive is itself is encrypted with a password in combination with a keyfile that I don't keep anywhere near the bank.  I have an encrypted copy stored within a personal ironkey, also using keyfiles that I do not keep locally or anywhere that the drive itself routinely travels to or gets used.

Just remember, you're much more likely to lose coins than have them stolen (i.e., forgotten password, hard drive failure, house fire, ruined paper wallet).  For that reason I always make sure I have 2 working copies which are physically separated.  I also have redundancies for the keyfiles, which are necessary to recover the wallets, but its easy to keep copies of those in various places since they by themselves are not valuable to anyone.  The keyfiles are not labeled as such, obviously (you can use any kind of file).