I use electrum (electrum.org). My private keys are derivable from 12 words. If you can safely store 12 words--which means not only not losing them, but also keep them from prying eyes--you can store BTC. Electrum can turn the 12 words into your wallet file, which contains many addresses, and allow spending from them.

You can copy wallet files endlessly, but you can only spend a satoshi (one hundred millionth of a BTC) once.