It's not just one steady downhill ride for leather after the car is new. Leather seats and upholstery need to be cleaned and conditioned to maintain their appearance and comfortable feel. Take a look at the before-and-after appearance in the leather seats of this 2006 Porsche 911.
OBSSSSD Leather Cleaner and Leather Conditioner are tremendous products for refreshing leather seats.
Both products are available here: https://www.autoobsessed.com/search?type=product&q=OBSSSSD+Leather
Products shown: OBSSSSD Leather Conditioner 16oz. and OBSSSSD Leather Cleaner 16oz.