Well how do you judge batteries that haven’t been around for decades?
I always find this to be a hard question to know the exact answer. Lithium batteries haven’t been main stream until the last 4 to 5 years. This doesn’t give the best source of information for life expectancy on the road. So how do lithium battery manfacturers know how long to warranty their products? They test them to simulate the real world use that the batteries can expect. Warranty costs can be exspensive, so I think looking at the warranty of the battery will give you a general idea of how long the manfacturer expects it to last.
A measuring stick from the real world for AGM battery life expectancy applied to lithium batteries
I have an AGM battery that was warrantied for 2 years but has operated for 7 years. This is very long for such a battery, but it does happen.
The difference with Lithium batteries
Lithium batteries are much more measured. The battery cycles, the number of charges based on drained percentage. This allows the manfacturer to get a better estimate on how long a battery can be expected in the real world. It is my guess (Only A Guess) that a lithium battery will last about 20% longer than it is warrantied for. Time will tell how close this will be to accurate.
Lithium battery warranties vary from around 5 to 10 years depending on the specific battery and manufacturer. It is our guess that lithium RV batteries will last about 20% longer than their warranty. So this would be 6 years on the low end to 12 years on the high end. How much you use and abuse your RV battery bank will surely play a part in how long the batteries last.