Just on CNN:
The MAS CEO declared during a press conference that the FDR / CVR - ULB maintenance records indicate that the ULB battery due date is June 2014.
At what intervals are the batteries usually changed? In general, how substantial (or how minimal) is the likely dropoff between the projected pinging duration (beyond 30 days) of a newly installed battery versus one due to be replaced soon? (I realize 30 days is the minimum requirement and that individual batteries may differ).
The Batteries have up to 8 years from new until replacement. Dukane allow for some storage though, and so the minimum you will get at point-of-sale is 6 years.
Unfortunaltely for the SAR effort for MAS370, it looks like these batteries (if the June 2014 expiry is correct) are end of life units, meaning that they will not last long beyond their certified 30 Day life.