If you are certain there is no ethanol in the gas you are buying, the only thing you have to worry about is condensation, and gummed up carbs or injectors if it sits without being started for long periods. I would still add some water inhibitor/gas stabilizer to every tank.
If it is possible you might be getting some ethanol, you would be money ahead to add an ethanol treatment to each tank.
I drained my gas tank in a Nitro I had a few years ago. The gas was purchased the day before. Put some in 3 different quart jars. 2 hrs. later in all three jars the ethanol had separated from the gas/oil mix, and settled to the bottom. You could see 1 or 2 tiny bubbles of water the size of a pin head on the bottom of the jar. I shook the jars around and the mixture turned grey colored, instead of the bluish normal color. It will not mix properly.
If you research it, you will discover ethanol blend gas starts to separate almost immediately. In car engines you can't see it in a steel tank. it is hard to tell it when a car is running. For some reason larger engines don't seem to have as much trouble running on ethanol as small engines.
I couldn't help but think the pickup tube is at the bottom of the gas tank where all the ethanol is settled without any oil mixed with it. That is what is primed into the primer bulb and carbs first. Pure ethanol!
Ask any small engine repair man. Lawnmowers, weed eaters, chainsaws, etc. Several have told me since ethanol has been added to our gas, their repair service has double in volume. All because of phase separation, and what ethanol does to most plastics and rubber.
I know there are some climates that have quick temperature changes or muggy, humid air. Those climates allow condensation to build up in a gas tank very quickly. And not everyone can afford to store their boat indoors. Others park in a slip which is even worse than the back yard.
I had trouble with the Evinrude 200 hp on that Nitro for months, until I found out about ethanol and phase separation.
I always add a good ethanol phase separation additive to slow the process and keep my outboard running good.
I run my outboard at least once a week, sometimes 3 or 4 times a week. So the gas doesn't sit very long.
I can afford a bottle of additive, not a new powerhead.
My 'SOSO' Humble Opinion.