Dale, just for comparison purposes, what sleep setting do you typically use with 10d?
As I recall, I normally used Sleep of 20. Here are today's 10d for direct comparison:
Sleep 15 fps 71.53 and
essentially constant.
Sleep 18 fps flips between 58.35 and 60.24
Sleep 20 fps 52.71 and
essentially constant.
I can't visually see any apparent difference among those, nor with any higher fps. The monitor is an Acer AL2216W, set to 1440 x 900, and 75 Hz refresh ("vertical sync").