"If it ain't broke don't fix it."
I still have the original battery in my 2013. I keep it on a Battery Tender brand charger. The only reason I would consider replacing my battery due to age (and no other factor) would be if I were going on a long trip to an area where it would be hard to find a replacement.
2013 XC Suede Nuclear Sunset
21" Conversion incl. ABS Module, Rear Shock and Forks
Lloydz HPT Cams
Lloydz Air Filter
Lloydz Timing Gear +4
31 Tooth Drive Pulley
Southern Motorworx Tune: 118.08 HP - 114.97 Torque (before 31 tooth drive pulley)