What brand and size, how long do they last, and how often do you fish.

My boat came with Continental tm-27 batteries. At 13 months they took a dump, hard. I replaced them with an upgraded version of that battery. tm-27-165. While they do well, I feel like they are starting to decline in lasting. This is at 11-12 month mark.

I fish almost every weekend, with the exception of some during the winter months. They always go back on the charger when I get done.

So ... in a month or 2 or 3 I will be looking for batteries again.

We have had the Everstart 27s from Wal-Mart. The key to trolling motor batteries is maintaining the water level. I went through several of the Everstarts before I finally was smart enough to realize I was causing the problems myself. Apparently charging and running them down over and over causes the water to deplete quickly. Use distilled water and keep enough water in them and you'll be fine.

The water level and charging before you put it up for the week is what is most important. I don't as much as you, spring to early summer, put it up in the fall (hunting season). I have gotten 3+ years on my trolling motor batteries before I had to replace them last year.

What he said. This was word for word what I have experienced as well.