Personally I've had great difficulty getting rid of Silverfishes. Despite plugging all crevices with diatomaceous sand, making sure indoor temperature does not exceed 18°C, removing any specimen on sight, I still encounter one every now and then just chilling on the wall or floor. They've eaten my underfloor isolation (the floor sags at those spots now), but other than that they're harmless - I can't imagine the horror if they snuck into my bed and bit me in my sleep. I would seriously consider throwing everything away and starting anew.