I'm a retired mechanic, a long time RVer and I have extensive experience with batteries. I'm not a fan of AGM batteries for RV applications. They work well in closed environments where fumes are a problem, in multiple positions and the are maintenance free. However they are expensive and usually don't provide as much cranking power as flooded batteries. You can also get a flooded chassis battery that is maintenance free. I recommend a good flooded lead acid battery, keep it fully charged as much as possible and try never to discharge it more than half way and you should get years of service from it. My chassis battery is 5 years old and still going strong. I have four 6 volt golf cart batteries for my coach, I dry camp some and I live in Nevada where they get both heat and cold and after 4 years they are still doing great.