Hi
$10 refill is good for 30 days, $25 will last 90 days. I apologize for any confusion information on that. Here is the refill info page that explains expiration dates at the bottom: How To Refil Your Account.
"Refill cards have varying expiration dates. $10 to $24 refill cards expire in 30 days, $25 to $99 cards expire in 90 days, and $100 and higher expire in 1 year."
Thanks,
Dmitriy