You can get a Battery-tender....not specifically that brand but any self-regulating trickle-charger will work.
we've installed the napa brand on numerous customer's cars through the years with great success.
you connect it to the battery and route a small connector out near the grill opening and leave it there permanently...then park where you can just plug it in to the "tender". all you have to do is remember to unplug it before you drive off...it feeds the battery only when the battery reaches a critical voltage, so it isn't "on" all the time.
or you can install a quick-disconnect to your negative terminal: just open the hood, unscrew the green knob and close the hood. screw the green nob back tight when you want to move the car.
I had a 5 year old battery in our 69 Roadrunner and forgot to disconnect it one winter. it sat for 5 months and fired right up, so it's not always the age of the battery but what the vehicle uses from the battery while sitting:
alarm/security system, "keep alive memory", modules, PCM/UCU's, radio (clock, pre-sets, etc), AIR SUSPENSION modules....anything that "stays alive" when vehicle is shut off.