Prepaid Breakage.

The concept of breakage is very interesting indeed, its where the carriers make their cream. To explain breakage or what is sometimes referred to as slipage we need to draw an analogy.
Let's say you pay for a gym membership but never go more than 4 times a month, the chances are that you not going to get fit and more so the gym is going to make money.
By nature people have an inate ability to always buy more than require. This fact holds true for prepaid, consumers on average buy more than they going to use and therefore unused credit often falls into a expiry position known as breakage. Other forms of breakage are loss of sim card where all credit linked is gone in one foul swoop.
The message of breakage is that before you buy your prepaid product be sure that you understand that expiry threshold terms and conditions. Carriers always publish this in the fine print as they shoot for high breakage and it does not pay them to disclose the high margin areas.