Cassandra Classic storyteller challenging only in the beginning?

[Jan2607]

I'm actually playing with Cassandra Classic on medium difficulty.
In several playthroughs I noticed that the beginning can be challenging with raids every few days. But now, where I'm 212 days in the game there are so much less raids. I think the last one is weeks ago. My colony is rich and big and prepared to fight, but no one wants to come. Shouldn't Cassandra progressively increase the difficulty?

[SzQ]

You can rise difficulty level or even change storyteller in settings.
Also
http://steamcommunity.com/sharedfiles/filedetails/?id=1277882177