In bitcoin-qt, when you FILE >> BACKUP WALLET, that's the same as copying your wallet.dat file, correct?
bump ^
Yes. But.. please heed the warnings above. A USB stick is not the best place to store your wallent long term. Make a paper wallet, I wont give you a full guide here because there are plenty around but basically to be supersure;
1) Make an ubuntu boot USB stick
2) get a second stick, goto www.bitaddress.org and save the page on it
3) disconnect your internet
4) boot pc with USB stick
5) use the www.bitaddress.org page to generate an address and print out the wallet details tab - make a note of the BTC address and put this in your safe/deposit box whatever..
Send BTC from your wallet to the address you generated offline, just dont loose your bit of paper or it is lost forever.
Getting them back is a matter of importing the private key on your paper into a fresh BTC wallet.