They're finicky about charging voltage , too low or too high kills them. In cold climates they can be weak , so you leave the lights on for several minutes before you start the bike and it warms up the battery. They can sit quite a long time without being charged. When they crap out , it's all at once , no warning like a weak AGM battery , so sooner or later you're stuck. Then there's also the occasional thermal runaway/bonfire. I just bought a new Yuasa for my 9 , they're all I will use any more , even cheopo , off brand AGM batteries aren't worth the eventual aggravation.