You are correct... Going back the available counters are much less than those on the real-time checks.
I submitted a request to VMware support and they pretty much confirmed all of this, and routed me towards an interesting document:
http://www.vmware.com/files/pdf/techpaper/VMware-vCenter-DBPerfBestPractices.pdf
This document explains a lot of those changes.
I also did not realize vCenter 5.1 has a built in calculator to estimate the size of the DB when upping the stats levels.
I just have to now figure out which levels I need for which retention periods and balance with DB growth, which I fear will not be an easy exercise. At any rate, thank you for your help.