Like guangzl1 mentioned, the only difference between a $25 refill that lasts for 90 days and a $50 refill that also lasts for 90 days is the amount of money being added to the account. Both $25 and $50 or somewhere in the middle will add 90 days to your account expiration date.
The 90 days could work in a cycle depending on how often you'd like to refill your account. For example, you could add $25 to your account, use it up within the 90 days, and then add an additional $25 to add another 90 days to the expiration date.
The 90 days could work in a cycle depending on how often you'd like to refill your account. For example, you could add $25 to your account, use it up within the 90 days, and then add an additional $25 to add another 90 days to the expiration date.