“The 7-day Caribbean/Mexico Travel Pass gives you 7 consecutive days of Easy Roam when you’re travelling in one of the eligible destinations. The pass will stay effective on your account for 30 days from the activation date. Once the pass expires or is used up, any further roaming will be charged at the regular rates, as listed on.”

Because it stays effective on your account for 30 days, you have to wait for those 30 days to pass before buying another 7 day pass.