Sometime between now and 100K you definitely need to have the upper timing chain rails looked at. More likely than not they need to be replaced as they are probably beer bottle brown. Once brown, they turn brittle and break easily, once they break that causes havoc with the chain. Your mechanic should be able to tell the condition of the chain while inspecting the rails.
Some folks state the chain needs to be done at 100K on the V-8's, others say 150K, maybe longer, as long as the rails are changed. The chain on the V-8 is a good 6 feet long and makes numerous turns and double backs compared to the 6 cyl. For a DIYer, the chain and rail replacement is not too difficult and pretty durn inexpensive, really cheap insurance.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.