djp
On 9th November you suggested active life of recorders on seabed could be extended by not transmitting active accoustic signals until active searching was observed. The degreeof extension depends on ratio of "listening" power drain to "speaking" power drain.I have no idea of this.
An alternative could be to eject recorders(with flotation device) when outside pressure corresponded to few feet of water. Problem would be demonstrating lack of "nuisance" events. You might like to consult with manufacturers of recorder packages.
Keith