I have the same address in blockchain.info in bitcoin-qt and in multibit
Then I have another one only in blockchain.info and bitcoin-qt
Another one in blockchain.info and multibit
And finally another one for bitcoin-qt and multibit
And of course I have addresses that are only for each wallet, so if I need to use my BTC on the go I send them to the blockchain.info address without the need to log in there because I already have it in my address book so I just move money between my wallet and they are in 2 places at the same time!
Well... that is really an interesting way to secure your wealth. Are you managing around a million USD in bitcoin ?