In reality, the turns per crisis is higher the more crises are active. My approximate phrasing would be "Crises take 5 turns to occur plus 2 turns for each existing crisis." but I'm not sure how you'd do it.
Yep, looks like I missed this when I made changes to the system. It's accurate to how it used to work but definitely not any more. I've got it on my list now and will see about getting a patch out soon. Thanks for reporting it.