Outer Limits 4x4 Board

I have just replaced my deep cycle battery with a new one as it wasn't holding its charge. It was about 3yrs old. I suspect its because the fridge only gets used occassionally and the battery dosen't like sitting there not being not used.
I have changed my driving lights and UHF radio over to the deep cycle battery to try and use the battery at least a little bit. I only put the fridge in the car when we go away on overnight trips.
Anyone else got any good ideas on how to discharge the deep cycle battery easily to help lengthen its life ??

I thought as long as it's kept fully charged then the a battery's life shouldn't be shortened? I'm sure someone else will know?

My aux (not a deep cycle) only gets used for about a week each year and is three years old. Had it capacity tested a few months ago and it read well above the CCA rating.

If you keep a battery at it's recommended float voltage (typically 13.4 - 13.5 for a flooded lead acid battery; after it's been charged fully with a bulk charger), then yes it's life is prolonged. However lack of use can also cause sulfation if it's kept on float forever

There are other factors which come in to play also under the hood - true deep cycle batteries do not like heat, they don't like overcharging, undercharging, or excessive current loads (in or out). A vehicle charging system is typically not well regulated and can overcharge batteries, or undercharge batteries - if they are sensitive types like AGM's, deep cycles, stationary batteries, etc. the battery life can be shortened.