I'm perplexed - My E@H total credits go up, but my average credits go down

Short answer none...long answer projects don't do what you are talking about. When your RAC, Recent Average Credit, goes down it means that over time you are doing less work now than you used to do. That could be because each workunit takes longer to crunch and yet they still give the same credits per task then your RAC will go down. Also older computers slow down over time, not much but over years you can see the difference. RAC is a coimplicated formula that essentially says last months credits count less than this months credits and last weeks credits count less than this weeks credits and yesterdays credits count less than todays credits.

Each Project provides a data file on their website that all the stats sites download, some Projects provide that multiple times per day while others only do it once per day. The stats sites then show those credits on their sites without us having to go to each Project to see them. The stats sites then parse the data to show the weekly and monthly numbers but they are not showing our RAC, they just divide the data they have gotten by 7 for a weekly average and I'm guessing 30 days to come up with the monthly average.

If you want to know the gory details about something, a search engine is your friend.  A quick google for "How BOINC RAC is calculated" gives a plethora of hits.  Interestingly, one that was quite near the top of the list was this thread right here at Einstein.

The thread starts out in a light-hearted vein and does contain some frivolous/misleading "information" but later on there is quite detailed and useful discussion by the people who have done the research - like Richard Haselgrove, Stan Pope and archae86 for example.  Richard is an IBT (International BOINC Treasure) :-).  What he doesn't know about BOINC is probably not worth knowing.

Personally, I pay little attention to RAC, particularly on the short term.  I set the <save_stats_days> option in cc_config.xml to 100.  The default is 30 and that's too short to properly see the trends.  If I have any concerns about a particular host, I use the statistics tab in BOINC Manager to eyeball the full RAC graph.  I expect to see lots of ups and downs so those fluctuations don't bother me.  If I see longer term trends lasting a few 10's of days or more, I will investigate further.

You will notice that Stan joined in 2005 so he had a lot of years contributing to this project.  Like many of us here, I'm guessing that he was well retired at that time and dedicated to 'giving back' to science in those areas of interest to him.  Those sorts of people tend to keep contributing while they are able.

In the early days, I remember him as a knowledgeable and passionate contributor who was really keen to understand how things worked 'under the hood'.  You can sense that by his reaction when he finally got hold of the full formula by which RAC is calculated.  I certainly don't know for sure, but I suspect that the "or worse" may be the true reason why he hasn't posted more recently.

BTW, you must have responded to my post immediately after I made it.  I did what I always do - reread the whole thing immediately after posting just to finally check for any typos.  I noticed the missing 's' on 'stats' so I corrected it immediately - but obviously not quickly enough since you have snagged the uncorrected version.  Just in case anyone tries to use that cc_config.xml option, it should be <save_stats_days>.  Anyway, it's always good to check the full documentation if planning to implement any of the available options.