The older the battery the greater the chance it'll go toes up. They often simply fade away but can give up and go dead in an instant
If you don't change it, it'll die 200k from the nearest bar. If you do change it the old one will probably have been good for another 2 years so whatever you do it'll be the wrong decision. Accept the inevitability of this.
More seriously, if the battery regularly goes too flat to start the bike after say 2 weeks of standing or less, then it's on its way out so change it now. You'll need to do it before much longer anyway so better to do it at home than being stuck in the middle of nowhere as unless your missus has thighs like a wallaby you'll not be able bump start a GS, especially on dirt.