The roll over is structured in such a way that keeping rollover data is the worst thing to do.
If you are in month A, any data carried over into month B will only be used once month B's data is used up.
Since you will be using B data, then A's data as you always use the current month's data first.
That means that when you are in month B, once you've used up all the data, you actually won't have anything left add to the rollover for month C.
TL;DR - the Axxess rollover is actually a double edged sword. To use the rollover data that you have saved, you need to sacrifice rollover data for the following month.
If you are in month A, any data carried over into month B will only be used once month B's data is used up.
Since you will be using B data, then A's data as you always use the current month's data first.
That means that when you are in month B, once you've used up all the data, you actually won't have anything left add to the rollover for month C.
TL;DR - the Axxess rollover is actually a double edged sword. To use the rollover data that you have saved, you need to sacrifice rollover data for the following month.