The handy little Firefox plugin seems to have new numbers every hour and a half or so...One thing you can do is check "This Month" and "All Time" which seem to be updated more often....Strange.
It updates about every 30 minutes or so. For some reason, trying different date ranges and choices can provide more current numbers. You can get 3 or more different results depending on your selection. Selecting May 3 thru May 10 can give you different numbers for May 10 than selecting May 8 thru May 10. The "today" selection is usually (but not always) the least current. I discovered this one day when my firefox plugin wasn't matching the adsense page.
Well don´t make my mistake... I just discovered the reaon for a huge discrepancy on my channel and aggregate data. I had added my domain as a channel, plus I had individual channels within my domain. I´d also recently made some design changes to the AS ads and so I was thrilled to bits to see my takings jump by 25%. What a plonker! When the aggregate refused to catch up with the channel data after three days I emailed Google who very politely told me that my domain and channel data were being counted twice. Oh well. There goes the Caribbean holiday for anothe year.