In the last few months, I've checked an /81 300D timing chain with 180K miles and an '86 190D with 150K miles. They were both right on the money. Both of these cars were bought used and supposedly had regular and frequent oil changes. This tends to suggest that IF the oil changes have been done there is probably no problem. But it sure wouldn't hurt to check yours.
It would be very unreliable to depend on timing chain tests done on cars other than on the car you're concerned about. Checking the timing chain is very quick and easy.
I'd suggest that you do it, if for no other reason to allow you to sleep better at night.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in