As a former boat owner my boat was kept on a revolving mooring, no connection to shore, no solar to maintain the battery bank. It would sit unattended for weeks, months sometimes, with no charging. The boat was dead. Nothing but a bilge pump hard wired to the battery.
Never had a problem. This experience is not unusual. People such as farmers & construction companies leave machinery unattended for months at a time.
This with wet cell batteries which self discharge much faster than AGM, gel cell or lithium.
Read the manufacturers instructions on care & follow them.
