Without going into all the complicated details of additions to my cat family, it seems to me that it has got harder and harder to introduce new members. I have plenty of space, and three of the cats go out for a few hours each day, but as each new one has come along the introductions get longer and longer. I still have one who lives in my bedroom after a year and is not tolerated by most of the others. Is this a normal phenomenon? I go through all the recommended procedures, and have tried re-introducing, to no avail.