Our OEM Deka DC-24 batteries (2) are 3 years old this month and so far I have not seen any decrease in capacity (150 AH for the cell). We dry camp a lot and are pretty heavy users of DC power; computers, TV and everything but the Air Conditioning and microwave. I have been waiting for a reason to replace them and so far they have been steady performers.
I do follow the recommended guidelines for recharging and discharge levels. The TM-2025 monitor allows me to be very cognizant of battery performance.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW