I am a serious bondage slut and have been lucky enough to experience a vacuum bed bondage session. It is extremely challenging to endure, especially when combined with some of the other activities you describe in your post. I was absolutely immobilized, couldn't move an inch. I can't even imagine having a milking machine used on me while in a vacuum bed.

I know a toy like that is very expensive, and difficult to properly use. Your subs are very fortunate to have such a well equipped, skilled and extremely beautiful Mistress to serve.