Yes not optimal to leave any battery permanently on a battery maintainer or smart charger. As you suggest George battery longevity is greatest when it's regularly but lightly used discharging from fully charged to say 90% then back to fully charged.
Leaving it long term on a float charge causes stratification of the electrolyte on a lead acid battery and this whilst it's in its most acidic fully charged state causing plate errosion. Some sophisticated chargers are programmed to run the multi stage charge cycle every 15 days ago causing electrolyte to be stirred to offset stratification. You can of course simply cycle your charger off then on to provide same every couple of weeks.
The policy I adopt is to use my vehicles at least once every three weeks throughout the year supplemented by 24 hours on a smart charger every couple of months. This undoubtably pays dividends. Remember also batteries are consumables though and a regularly used one on easy starting car will mask the inevitable ageing process as sulphation of plates reduces battery capacity. Warning signs are when put on a smart charger it reaches fully charged in short order.
