I'm using the DCM 475, got it from Teksavvy when I came onboard with them Sept/2011. Since it was received from them, I would have expected it to be current (re: firmware).
My disconnects are more frequent than 7hrs, probably every 2 hrs or so.
I haven't been online all day today or anything, but was playing a game online for around 3 hrs from 11:00-14:00 today and had two disconnects. Just got on this evening at 19:45, been on for almost an hour and just got a disconnect.