No. You may opt for that package anytime during the day. As for 12 and 24 hour packages just multiply accordingly as the 6 hour package is specially priced. In fact, for any duration more than 1 hour you are already getting a discount and the longer the cheaper.
(2+1) = This is available to categories other than China, local and exotic. When you order two hours you get one free but number of cums is still based on two hours.
(3+1) = This is available only for China. Although you only pay less than three hours you will get an addtional hour free. Again the number of cums is govern by the actual hours you pay.
(6 hours) = For non Thailand, Indonesia, Laos, Vietnam and Phlippine only three cums allowed. As for China it is actually a (4+2) hence 4 cums.
