I don't know that you've necessarily been 'lucky' mattsuzie. MB doesn't list a change interval for the timing chain, it's deisgned to be very durable with (surprise!) regular maintenance (regular oil changes).
I've always understood (hearing from two well-experienced Indies) that only if the chain stretch is over 5 degrees should one replace the guides and tensioner - if the chain isn't worn, don't change it!
Now personally at 200K, I'd feel pretty comfortable chaning it all out, but I hear a lot of people here changing the whole shebang at 100K (or a little over) for 'peace of mind'. Unecessary imho, but then we all have different comfort levels of preventative maintenance...
'95 E420 - 'Shadowfax
'92 Volvo 740Turbo Bard
'74 240D - 'Ol' Green
' 4spd Manual 104kmi. (sold
'77 300D - 'Red
' 223kmi (sold)
'75 240D - 'Bianca the Blue Bomber