OEMs were 6 NAPA 31s - nicely located low in the frame under the slide out storage tray. If cared for they should last 6 - 10 years. If the coach has been left sitting for long periods with phantom loads and battery switches 'on' the batteries won't last long when boondocking. If consistently 'plugged in' the batteries will support the electrical needs without problem.
Other than "dealer or owner neglect" I've not heard of any issues. Are there other specifics you'd like our replies to address?
2015 Itasca Ellipse QD | 2014 Jeep Grand Cherokee