sounds like you've been pretty lucky.
me and my buddies had about 6-7 invasions so far.
once by greydwarfs, 3 times by trolls, once by surtlings and the rest by draugr/skellies.
they never managed to actually do any damage to our base though, so there's that.

oh and this was long before we reached day 180, and we're currently on day 223.
43 days without a raid is pretty lucky, but your luck is even better it seems