They are available as soon as you transfer them....either on line or by phone. If they are showing up on-line as available but not on the card yet, as soon as you make the request it happens. If you are asking how long does it take for them to get credited to you to begin with ..... it can take 6-8 weeks for them to actually become "rewards".
Right now, I have a balance on my card of 11, I have a balance in my account of another 10, but I know they owe me still from what I spent a month ago....I can transfer the 10 to my card online and be able to use them immediately....
But, I do get annoyed sometimes on now long it takes them to post the rewards to my account to begin with.