I used to think what you said about it all accumulating in the current period bucket, but try it out on a backup of your data, and you'll see that it goes into the proper buckets. I have one or two clients who, upon beginning a new year, immediately advance all of the period end dates by one year, and then they don't have to remember to do Period End at exactly the right time.

However, the system is not smart enough to recalculate if the period doesn't exist at the time of posting. So don't think that just by changing the date to 7/31 and 8/31 after you have posted July or August activity that the figures that show in 6/30 will somehow get adjusted.

Nothing else is affected besides the sales history tab.