Stop worrying. So long as you have a good regulated battery charging
source....shorepower or solar
or whatever....your deep cycle batteries will be just fine.
In order to prolong their life, however, it will be good to use a sufficiently high float voltage to stave off the almost inevitable sulfation, and it will be good to equalize them (controlled gassing) periodically to help knock off the PbSO4 crystals from the plates and stir up the electrolyte to avoid stratification.
Even at dockside, it's possible to "exercise" your batteries, and that's a good thing. For example, turn off the charger for a day or two or three and run everything from the batteries. Then, charge 'em up and you're good to go.
My six year old T-104's still test like new, and they're mostly on shorepower 24/7.