Does your SB900 get tired at the end of a long shoot?

I keep having an odd experience with my SB900 on jobs, long jobs. By the end of the night, usually a 10 hour day of shooting, my SB900 just seems to get tired. I have to keep boosting the power settings up. Batteries are replaced and fresh, the temp gauge is fine, it just seems tired and puts out less light... about the same as me at that hour...

Anyone else experience this?

I may try a Quantum this weekend and see if there is any difference.

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Dennis
http://www.dennisleephotography.com/