Its been about 12 hours and I have no confirmations.

I know that most bitcoin wallet clients will return an unconfirmed transaction to your wallet balance after a few days, but when does blockchain.info do it?

I accidentally left out a miners fee for a transaction, which I sent through blockchain.info's "shared send" service. Its been about 12 hours and it is still unconfirmed, also I am sending it to bitstamp, which requires 3 confirmations.

I read the following post about double spending: https://bitcointalk.org/index.php?topic=231309.0

 I am in the process of downloading the blockchain for bitcoin-qt, is it a good idea for me to double spend this transaction? I am worried it will takes weeks for me to get 3 confirmations and I think once I get at least one confirmation I can no longer double spend and will have to wait for the 3, which could take forever!

What are my options!