Friends of mine have owned Mason''s and I have crewed and cruised aboard a Mason 44''.
They are great boats, well built by PAE and certainly are very habitable. Depending on how your''s is equipped you should be very comfortable living aboard. However a 40'' boat,regardless of size,can get pretty small after an extended period aboard especially if there are more than two of you. PAE is also very interested in hearing from owners or potential owners, so give them a call. They can probably put you in touch with other like minded owners. Good luck!