Starting January 25th, all AT&T Mobile Share Value plan customers will have this feature automatically added to their accounts at no additional cost - you do not even have to call in to activate it. This is not a "limited time offer" like the double data deals, but rather a new standard feature from AT&T.
Rollover data is being added to all Mobile Share Value plan business and consumer accounts - but does not apply to data-only plans that do not also have at least one voice line sharing the data. This means that AT&T customers with just hotspots or tablets on their Mobile Share plans will not benefit from rollover data.
A bigger catch - unlike T-Mobile's "Data Stash" program which keeps rolled over data accessible for a year before it expires - with AT&T, any rolled over data is only usuable in the very next billing cycle. And, if you increase or decrease your monthly data level to adjust to changing usage need, you will lose any currently banked rolled over data too.
The most annoying limitation that comes from the one-month expiration is that regular monthly plan data is consumed first, then rolled over data. So if you have a 10GB plan and only use 2GB this month, next month you will have 18GB available. But to tap into the extra 8GB, you have to first use up your entire 10GB of plan data - meaning the following month you'll have no data rolled over at all.
And if you accidentally go somewhat over and end up paying a $15 overage charge for an additional gigabyte but don't use it all, any remaining data in your overage gig will NOT rollover to the next month.
So in practicality, on AT&T you will only be able to utilize rollover data every other month - at most. This makes AT&T's rollover data program substantially more limiting than T-Mobile's.
However, unlike T-Mobile's per-line rollover - on AT&T you can use your excess data on ALL all the lines sharing the plan.
AT&T is also still continuing to offer double data deals for data plan 15GB on up (doubling them to 30+ GB), making the second biggest carrier in that nation a very attractive deal to data-hungry RVers. And now - if you're out of an AT&T service area one month, you can rack up a lot of data to use the next month when you're back in an AT&T zone - making the larger 30+GB AT&T plans even more appealing than ever.
Now that AT&T is on board, will Verizon be able to resist the pressure to also offer rollover data? We hope not - competition is a beautiful thing!