a battery is required as a buffer for the converter.... the converter will work without a battery, but the electrical system is more susceptible to power surges, annd its harder on the converter if used long term without a battery connected...
BUT, as you say that neither the shore power or the battery is connected when you are away from the trailer, which is totally fine, but in a normal operating system, there should be no need to disconnect the battery. but if you choose to have it disconnected, there should be a battery disconnect switch installed on the trailer somewhere....
keep the battery in the rv and connected when plugged into shore power. theoretically, the battery should last for many years if the battery is never really used because you are always on shore power.... batteries have a life span that is counted in "charge cycles", and if the battery never runs low, and never really needs to be charged because its always topped up, the charge cycles are not being used up.
depending on the technology of the batteries and the quality of them, the charge cycles can range from 200 to 800 cycles, and there is also a thing called sulfation that affects all batteries, but liquid cell batteries are most prone to age related sulfation even when all other parts of the system is proper....
