My starting batteries (Interstate 31s) we're original (11 years) until last week. This is longer than any battery has ever lasted for me. Because they still tested good I was not going to replace but I was able to work a deal where I could keep them. When I get home they will go in a 24V machine to see how much longer they will last.
OP if it passes a load test and all the cells test close to 13 with a hydrometer I'd keep BUT I have a large house battery bank I can connect if it did not start by it self so I could get some place to replace.