I have been wondering that same thing about your sitch. I think you "acting as if" serves a purpose, but if it seems too forced or phoney it won't work. It is ok to sometimes say you are tired or finding the situation hard to deal with. Just as long as it is not coming across in a "reprimanding" way. Just firm and matter of fact.
I also agree with Sandi that it may be time to be less accomodating. I know I started doing things like that in my sitch... just going on with life with the kids almost as if he didn't exist. He would find out we did fun things without him or he would come home to an empty house because the kids and I were out for ice cream without him. When he would be disappointed I would calmly and matter-of-factly say "It is hard to know when you will be home these days so we are just doing our own thing. You are always welcome to join us if you are around." Those things did have an impact...
