Originally Posted by xyzzy
T-Mobile is pretty good in populated areas. On a pre-pay plan, if you buy a $100 top-up card the funds do not expire for one year. Otherwise I think you only have 90 days to top up again.
Once you've purchased $100 in airtime (all at once or in increments) any added time is good for a year, and then is extended the next time you top up.