The only reason I can see to go back to your DME for anything is replacement supplies. A check up seems like revenue ploy unless they upgrade your machine to one that actually gets some good download information (highy unlikely unless you have had your machine for a few years as that is the only way...

Don't you just love spending the night at other peoples house? Why can't it be the same as yours. The best is when you go to take a shower and you never know how the hot water works and..you know what happens next.

I have an Idea. Try smelling the air that comes out of your CPAP machine. Or have your wife smell it (maybe you're used to it). Maybe it stinks...I could be dirty, or mildewy or something.