Yeah, usually I use water that's as hot as I can get out of the faucet, because that typically works faster and doesn't harm the cards. And let the cards soak as long as necessary, replacing the hot/warm water if necessary. Here is a pretty detailed how-to post I wrote up a few months ago, based on 20 years of soaking trade cards:
http://net54baseball.com/showpost.ph...70&postcount=7