DO NOT consider a lithium battery, while they are great and have their uses, if mis-used they can be a bomb. Never use the motors charging system to charge a lithium battery unless a professional sets up the system! Lithium batteries need special chargers and must be handled properly! Any mistakes can cause serious damage instantly.
Over the years, I have good sucess with Walley World batteries, getting warranty claims have never been an issue, in most cases they never check it, just swap it for a new one. Also had good sucess with Menards batteries, there to warranty claims were easy. Most marine/ motor home type batteries have a poor warranty because most folks do not maintain there batteries properly and the mfgr knows that. I keep up on my maintenence regularly and use a battery maintainer over winter storage and my batteries normally last much longer than average. I have a small wheel chair battery that I bought almost 7 years back, cost 38 bucks shipped to my door, I use it for my lawn sprayer and to run my electric trolling motor in my pond and other misc uses. Good as new today as was new, but has been taken care of !!