Deep Cycle Batteries

Mine last me 6 years...and I dont take perfect care of them either...Good...but not perfect

It depends on how deep they are cycled. Shallow discharge gives the greatest life span.

How high is up??
There isn't a stock answer for your query. With regular use and never allowed to run completely down and regularly topped off with distilled water when needed and when not in use completely disconnected from the RV or use a trickle charger, they should easily last 4 to 5 years. Violate any one of the above conditions and you shorten the life considerably .

If you maintain them properly, do not do many extreme deep discharges, and use a 3 or 4 stage smart charger to charge charge them, you should be able to get at least 10 years out of them.

I,ve got two interstate batteries four yrs old and still read 13v. its more a matter of a little maintance now and then ,that will pro long there life.