I have been working with some of long exposure shots with the 7D.
I am not impressed.
I am still tweaking the settings to achieve the highest quality image. It is difficult to get clean, low-noise images when exposed over a long period of time. Especially with 30 minutes plus.
I am trying out shots that are 60-90 min+.
Because of a sad anomaly in my 10-22 lens I am using an aperture of f/9 or more.(More on this situation later) My ISO is never higher than 800.
Still pretty sketchy. Lots of noise. I have yet to analyze the RAW images. They may have been kinder to the information. but for now I will leave you with this image I took a few nights ago.
I napped for an hour and a half in the cold and wet wilderness as my camera took the exposure. Interestingly after the shutter was closed it took the camera over two hours to finalize or write the data to the card(266x Kingston). I am not sure exactly how long it took as I went to bed and it was still writing 2+ hours later.