When a friend you referred signs up, they can start watching immediately. They are sent an activation link which they need to click within 24 hours or they will no longer be able to watch. You will not see a DVR point in your account for your 4 hours of additional DVR time until they click on that activation link.
If they have clicked a link and you still did not get credit, they may have not used the link you sent them originally to sign up. If this is the case, please let us know by opening a ticket so we can give you your DVR credit.