They say these M103 timing chains last "forever".
Mine has approx 180k miles, and seems perfectly fine, with no noise, no visibly over-worn guides, no visible cam-timing change, etc.
Oil changes every 3-4K.

But, should I roll a new one in, just for preventative maintenance after 18 years? Not a lot of cost, I can do the job myself.

I had a belt tensioner break in half and strand us last year, so I'm sensitive to these catastrophic failure potentials.

DG