i have a couple of these going again ... on my best 6600 @3.5 it is 10 min per frame, and on the next best @3.2 it running 11 min per frame.
I think Shell quoted a 6 Min time but i am wondering if he may have confused it with a 30xx wu? He would need to be folding around 4Ghz or more to get that kind of frame time, assuming frame times are consistant across 2605's. I do recall Shell had a very nice OC on his 6300.