I have tried many projects.

Einstein@home is one that badly overestimates its work upon download. I recently noticed 16 hours for one workunit, even though it only requires a very small part of that to complete (on this computer). With several workunits, that means that your queue will probably already be full of Einstein, based on the estimates. Once they run farther or complete, more work could be given to WCG unless Einstein fills it up again.

Some readjustment of resources between projects may also have an effect, but if it's full, it's full. It may take a drastic change for these two projects to share, like 90% WCG and 10% Einstein. The default is to give you "100" for each project. With two projects, each gets 100/200, or 50%, unless modified.

Primegrid is another project that behaves this way --- 29 hour estimate for something that runs in 10 minutes.

That problem eventually cleared itself up. Alas, Einstein@home is not restarting every ten minutes or so, and getting nowhere. (I've had it finish a unit before, so I know it can.) I'm not asking for help on that here, of course, and have asked about it there. Thanx, however, for letting me know that it's neither uncommon or a problem.