I have 4, group 31 yellow tops in my boat, bought in 2009.2 batteries are in the rear of the boat and run the 5.7 main engine, sonar, kicker, lights, radio, and 4 electric down riggers. They are still going strong.
The yellow tops in the front of the boat run my electric trolling motor and have been heavily abused.
By my calculations, they have run down to 12.1-2 volts 210 times and are still going strong.Just got back from a fishing trip where I ran the 2 yellow tops down to nearly nothing 10 days in a row. Hooked them up to my 30 amp speed charger for 4-5 hours,took them off the charger when they hit 13.25 volts and they were ready for another day.