I've had timing chain cover leak fixed at around 85K, so I didn't worry about the other internals.
Car is over 110K now, but I still have no worries regarding timing chain, but I also am religious about the oil changes.
No head gasket issues yet (knock on aluminum alloy), but when it does happen, I will get the chain serviced as well as other items when the head is removed.
If you want piece of mind though, go ahead and do both the chain and gasket now, so no worries for another 100K or so...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car