Presumably when any of those things happen, that's when you bring it in-house.
When you are raking in profits, you'd better use some of them to secure your business and make it independent of such risks. Which is the point the blog post seems to be trying to make.
Sometimes though you can make do with something significantly simpler if you restate the problem slightly and move the pieces around.
You might be able to do the core of the job with a cron job and some command line tools rather than the fancy SaaS platform with graphs and everything.
Building on top of the fancy SaaS APIs and then trying to scale down when you want to move away is a lot more difficult than starting with the simpler approach and then scaling up when you really need that extra functionality.
Believe me, I've done it in both directions.