I replaced my 2014 battery at 3 years ... it continued to read "100%" at dealer and they said it's fine, but didn't want to risk it. I could tell it wasn't holding charge as well based on how the smart charger reacted, (and how hot it was getting). Plus 2014's used a poor choice of battery (FLA) ... the new batteries are AGM which are superior in service life.
2014 Ghibli SQ4
Grigio Mareata // Cuoio-Black Extended Leather Interior
Cold Weather - Luxury - Sports - Premium packages
20" Urano Polished Summer//20" FT-6 Gun Metal Winter
Gtechniq professional // 3M Crystalline 50%