Normal difficulty, no sieges, raids, or snatchers; after the very first raid. 11 total years of gameplay. That was for the first fort I played in the world.

For the second fort, I moved much closer to the goblin civ. Pillaged their sites. No sieges, raids, snatchers, ever. Not even 1.

Turn off raids in the difficulty options, get a siege the very next season. But this isn't an ideal fix, I like the smaller raids and snatchers.

Another issue, I have 2 forgotten beasts that seem to have bugged behavior. They're just sitting on the edge of the map.