I think claiming that an ULB with a standard 30-day battery would still send out signals after 90 days is a mistake. Sure, Teledyne Benthos has a 90-day ULB model ELP362D available, but it only works for 90 days if an optional lithium battery is used. Standard battery life is the same, 30 days only.
http://www.benthos.com/_doc/main/Bro...815__rev_L.pdf (see page 8)