Wait really? The email I got from them made it sound like it would roll over forever. I'm gonna have to go read the fine print now. That's a big bummer if you are correct.
Yeah it is only month to month (previous month's unused rolls over to the next month only).
I think AT&T only rolls over data to the next month, so you aren't actually accruing anything. Unlike T-Mobile, who I believe roll over data for up to 12 months.