Some are disconnected totally as in the cases the car might become a fire hazzard in it's storage location. On most or the cars I usually install a post disconnect switch. Can be had very cheap now compared to first introductions. Although since about 1955 cars are fairly well protected by fused circuits. Others batteries are still connected. your right of course as a clock circuit even makes a small drain. Suspect batteries are sulphating bad. 1.5 amps trickle seems a little high but if you are not experiencing any damage it is obviously ok. Most trickle chargers my friend has deliver very little by comparison. sold as specially item but basically 12v ac adapters delivering about 500ma direct current available at yard sales for about 50c each. Some of my cars are not used for two-three years or even longer and they are the reason I want to find a better storage method if possible. Will probably try dumping the acid and store the battery upside down so any internal acid remaining will clear the plates. Just broached the subject as sure others are in simular situations. I may be pretty certain I am going to use a specific car next year but when the time comes am commited to something else and never get the chance. Best laid plans of men and mice I suppose.