Optimizer question - swapping algorithm?

We currently have optimizer set with a workload analysis period of 1 week and an initial period of 1 week.  When looking at Performance Manager, I've been noticing that we still have some disks that are much more heavily loaded than others when I look day to day.  These are 15k fibre drives.  When I look at the average scsi commands they say 70, but then I look at the graphs for each day and some go over 150.  I'm concerned that doing it over a week is not coverying my IO patterns enough to keep it properly balanced and was considering switching to a shorter interval.  What are the tradeoffs when I do that?  It seems like we've kind of stabilized right now and haven't been having too many swaps these days, but the load is certainly not balanced all of the time.

EDIT: Ok, I reread this today and I realized I made it overly complicated.   Here is the quick and dirty version.

We currently have a workload analysis period of 1 week which still seems to be leaving my load unbalanced on a day to day basis.  What are the tradeoffs to going to a smaller analysis period like 1 day?