I always us 95 or greater. Motor always runs better and better starting.
During the colder months when the boat is not used so much, I do not leave a large amount of fuel in the tank.
Start the motor every month and run for 1/2 an hour.
So far, touch wood i have never ever had a problem. But not saying that I will ever have an issue, as I may have a dose of bad fuel.
I work on the principles of good duel batteries, good servicing and maintenance and hopefully I reduce the risk of operating machinery in an hostile environment.