From my experience, by far the best thing you can do with NiMH cells is to equalise them regularly.
I've never noticed any real change in performance if I'm running off a fresh charge, a top-up, or a partial dump and charge.
The drop in performance for me comes from when the cells are not regularly equalised - especially if your cells are not brand new or "matched" to begin with.
My 3700's get used once a week (until we come to the regionals
). They get charged on a Tuesday night or Wednesday afternoon (owing to time constraints), given a top up just before using them Wednesday night, then after the race I leave them as they come out of the car. I know they don't like to be left flat, and as the self-discharge rate is higher than that of a NiCad, it seems logical to leave them with more than their residual voltage in. The following Tuesday or Wednesday I will discharge them at 20A on my Eagle CDC to a 5.4V cutoff, then equalised on my LRP board (a good use of £15!).
They are just starting to lose their punch (more noticeable as I race 27T) but considering they were bought early 2005, are used weekly, and have done 2 seasons of S E Regionals, I don't think that's too bad.
Going to invest in some 4200's or 4300's before the 2007 season though. The 3700's will be relegated to 4 cell oval duty!