It's interesting to note from the Boeing table that the DC9 is "King of the hill", far above the rest, with the B727 not a bad second place holder.
The highest time DC9 has exceeded 120,000 hours at last count, possibly somewhat higher by now.
It was said to me my a Douglas sales rep at the time of a contemplated purchase, that the worst favour Douglas ever did for themselves was to build such long life aircraft. Better to follow the Boeing "trash 'em and buy a new one" policy.
Now that the DC9 family flies under the Boeing flag as the B717, I privately wonder (cynically) what Boeing have done to reduce the B717 life cycle.
Regards,
Old Smokey (who flew a lot of DC9s, but now puts his butt and trust in Boeing)