Yes, leave the series linking cable intacked. Many boats have critical loads thats are connected direct to the battery, like the auto bilge, anodes and CO detectors. On smaller/trailer boats, disabling the auto bilge can be a disaster over winter. Ever the the moldy interior when the owner pulls the winter cover off to find the boat has been filling with rain water? Or a wet-slipped boat goes down because of collected rain. Your choice to disconnect the critical loads. However, you are better off the just disconnect the main grounds off the banks. This leaves the seriesed batteries still connected as one large 24V battery.