The problem might be that your looking at folding like you do at Hashing.  They are totally separate things.  When hashing, your rate pretty much can stay stable from now til the end of time, because your doing small calculations over and over again.  It never differs.  In folding, sometimes a single fold will take 1-2 days, If your folding a 70k workload and it takes 0.75 of a day to finish it, your days will look like 75K / 150K / 75K / 150K.  If however you get put on a different project.  Say folding for a cancer cure as opposed to folding for a cure for Malaria, the calculations will be way different, and the time it takes to complete will vary dramatically as well.  The work units are set to pretty much equal out overtime.  so in the case of a 75K / 150K flip flop your avg is 112.5K per day