Verlander : 6.57 innings per start
Greinke: 6.34 innings per start
Cole: 6.23 innings per start
Ryu: 6.7 innnings per start
Kershaw: 6.5 innings per start
Buehler: 6.1 innings per start
Note: in my calculation I removed the game in which Ryu pitched 1.2 innings and left with the groin strain as that is more relevant to a durability question than ability to go long in a game. With that game Ryu's average is 6.4.
Kershaw literally has the longest active streak right now of pitching 6+ innings.
That's good to know. Not sure why it felt like they couldn't stay in long.