Odds are that they are breeding somewhere in the house and are not “sneaking in” en-mass from the outside.
They are there because there is something for them to eat or to lay eggs in.
Look around closely for where they may be breeding.
It can be a dead mouse, rat, squirrel, bird, etc. in the attic, in a wall somewhere. Or some food product that slipped behind or under something. Maybe a spilled beverage.
My sister complained about these the other day,
I told her it was because she voted for Obama.