bucktruck: I think it would be preferable to listen to the folks here who have lots of experience with your type of truck, and its 6 volt system, versus the good intentions of the guy at Advanced Auto.
I tested a few of those little (ie cheaper) battery maintainers a few years back and found that they were not very good at their intended job. Their goal was to keep a battery charged when the battery wasn't being regularly used. The simple problem that many of them had was that they were not "smart" enough. Their processing ability was pitiful . They often trickled a charge long after it was needed, and thus would kinda slowly cook the electrolyte from my batteries over long term.
I would recommend a better 6/12 volt smart charger. I had good luck with older Schumacher 15amp XCS15 and the SC1359. The smart chargers will do most of your 6v &12v automotive, lawn , or marine battery needs. They are "smart" because they have better microprocessors to sense the battery condition.
I do not leave the smart charger ON for more than a day or so because its normally not needed.
I do disconnect a battery cable from battery when I store the truck for a longer time. I do maintenance charges with that a cable disconnected to isolate the 6volt battery.
If you need more garage starting ability, there are still some big 6volt /12 volt starter charges on the market. They can give extra amps to start your 6 volt.
Smart chargers will not fix a really bad battery, or fix corroded wiring & connections, nor a badly worn starter. They will keep a good battery in good condition. Trusting your 6volt battery when you first go to start your truck can lead to helping you find the true source of a hard start problem by eliminating battery suspicions.
