My battery is almost 5 years old as well and still cranking strong. I also use a battery tender but I only hook my batteries up once, sometimes twice a month. I let them charge for a day or two and then do it again 3 or 4 weeks later. I also ride at least once a week year around unless the roads are caked with salt and it hasn't rained to wash it off.
2011 Cross Roads Sunset Red
OEM short windshield, passenger backrest, crash bars, saddle bag bars, heated grips, vinyl closeouts, tachometer, ambient temp, LED headlight, luggage rack. WD lay down licence plate.