Whats the life span of marine batteries? Got a stow dual purpose batt, only run the engine and tilt,trim motor off it.

charge it after each use ...will last a long time ..
do not depend on the engine run time to keep it fully charged

2 years maybe more, maybe less depending on how you maintain it.
Check the water level regularly. Keep it above the lead and use distilled water, not tap water. Fully charge it after each use and every couple weeks when not in use.

thanks for the info fellas.