I don't know if it's RNG or a Seed choice...
I had playthroughs recently, that raids didn't happen in 100+ ingame days and suddenly the AI realizes that i am left in cold without food or rested buff and decides to launch a Pack attack on me.. fun times :)
Other playthroughs i got raids like almost every day. While this was annoyng, i farmed a lot of balls... ermm.. i mean eyes and other useful stuff.
Frequency of events made me never drop my guard.

Advice: Never let your guard down, even if raids are not happening for a long time.