I completed some offers for the 360elite4free.com site. Only 4 credited instantly but some I signed up for I got charged but never received an email for them. I also go the "Sorry but your card was declined" page but still got charged by the sites (I think stamps.com was one of them).
How long does it takes to credit?
As a good general rule, I would say that most offers will credit within 7 days if everything is done correctly (and occasionally incorrectly). After that, you may submit a manual credit request usually.