The I-wireless policy regarding your expiration date on your prepaid airtime is to subtract any time you have left when you add additional airtime. Any unused minutes will roll over but not expiration time forcing you to either use them or let them pile up.
I contacted I-wireless regarding this and they politely explained to me that this information is on the back of airtime cards. They could not however explain to me why this information is not disclosed before or during the purchase of the phone or the service. An airtime card is not required when the initial purchase is transacted.
This information is purposely withheld and you do not find out until you have already purchased their phone, which can't be used with any other service, and activated their service, which lures you in with free minutes to get started. In my opinion, the act of purposely not disclosing this information prior to the purchase is perpetrating fraud upon the consumer.
Review about: Kroger Prepaid Card.