Sky VIP offer: ''sorry all codes have been claimed''

[EveryonehatesChri]

Today I tried to redeem a trial offer (STV+ 3month trial in this case) which is due to expire shortly and I received the above message. This message appears to come and go depending on whatever content is offered. Will there be another opportunity to take Sky VIP up on this offer or is it no longer available to me? Also what exactly does it mean; ie are there only a select number of redemption codes available at any one time? Many thanks.