Actually that is not true and in the release notes it says everyone gets 5 tokens which are used to either do a challenge (for F2P and Premium players) or used for one-time use items in the challenges. (everyone) Premium get and unspecified amount of extra tokens.

PS. You can read the notes at http://forums.ddo.com/showthread.php?t=206066 .

PPS. KookieKobold says you get 5 attempts (which is one per token) at a challenge per day for F2P & Premium players at http://forums.ddo.com/showthread.php?t=346923 .