doubtful, they do not like being discharged. if it had been on a battery minder, i would be tempted. i am happy to get 3 years out of a battery.
I got 5 years out of a DieHard marine starting battery (was still great when I sold the boat) and 5 years out of a DieHard deep cycle (VERY light use). Actually still have that one and it's still in use. I never stored them on a maintainer but they weren't fully discharged either.
I have the opportunity to pick up an Interstate 27M marine/RV deep cycle battery, has been sitting without charge for 2 years, the owner wants $20 for it. Would you think the battery is still good if it were stored properly?