Yeah, my biggest beef is the number of 'applications'. The container claims 14 doses but in reality it's 10 or 12 at best. I think the reason for this is that the aerosol propellent spills or overflows whilst filling the applicator. That results in there being insufficient 'power' left when you are expecting to get more than the measly 10 doses. Sometimes I have to remove it halfway during filling to give it another good shaking.
I don't think the foam actually loses any of it's strength though, maybe you're not shaking it enough (I give it 10-15 vigorous shakes) If it was diluting they would have to yank it off the market. I've been using it on and off (mostly on) for the past couple of years and barely it keeps things under control and I still have to resort to bouts of prednisone as well for a lot of the time. The good thing about it is that it's dead easy to retain compared with the liquid enemas.