Calling Roomba owners - having just become the proud owner of a roomba i just have a query hopefully one of you established users can answer!! I heart my roomba already but wondering if I leave it to its own devices would it really cover more than one room if i left the doors open or just end up not doing one room and staying in the other? i know, i know , get a life and all that but was thinking it may be better to just do one room at a time? TIA !!!