My cam chain started rattling around 50,000 - 60,000 mile mark.
The bikes now done 78,000, and I haven't changed the chain. The chain is original to the bike.
I'm not suggesting you leave it, but if my experience is anything to go by, it may well last several more years.
I caveat all that with: I think the noise is cam chain rattle, because it's coming from the right place, but to be honest I'm not that good on noises.