Nick,
The instructions that you get with the BB explicitly describe that shutting down the electrical supply for long periods will tend to degrade the battery life. It has been discussed in these forums a few times that the BB could be used as a temporary "controller" of sorts by cycling the power on and off to reduce the Vortech to a 50% state and thus control them in a rudimentary manner without the danger of code corruption.
I bought into that and purchased two BB units, only to find that using them in that manner would greatly reduce their effective service period. I have now reverted to just using them as designed, for battery backup, and I recommend that you buy them for that feature, not to control your pump(s).
Also, there are no indicators on the BB units as currently being sold so I don't think there is any effective way to monitor the battery life at the user level and really know how long they will last and what draw-downs do to the battery.