Yes, this ^
If your just positioning your boat to cast or work shorlines etc....a battery will last a long time. Im willing to bet that the guys who say they are getting more than 5 years out of a battery have never run them down, and don't fish nearly as much as I do, because I have been burning up batteries for a long time, and there is no way to make them last longer than what they do, the way I use them. Running them flat every time kills them, period.
I get mine from my local battery shop. Kawartha Battery in Peterborough. I don't even care to shop around for a price, because its a small family run business, and, well, they are just great people, so I prefer to support them rather than some CEO of costco.....just my choice.
I paid $175 all in for a 31 series deep cycle.
S.