I suppose there are many ways we can try to save the paint on our palette... and I have probably tried most of them.
I'm not crazy about the idea of freezing the little blobs left over on the palette... I know freezing can change things chemically.
The idea of covering with water never went far for me.
Here's what I have been doing for quite a while now.... I cover the palette with a double thickness of plastic wrap and then cover that with foil. I have used the same sheet of foil for a very long time. I now have some heavy cardboard that I have wrapped with the same foil I started using a long time ago. (I'm showing the foil side up, but actually the foil side always touches the plastic wrap.)
I like this system.
However, the dry summer heat here usually makes the paint set pretty quickly on the palette... usually after a few hours of painting. Even the cadmiums don't usually last much longer than a couple of days on the palette.
My dabs of paint are small, but that's mostly because I prefer to refresh them after a bit in these summer months, rather than work with crusty tops and thick paint...
or I sometimes know that I will only have a short bit of time to paint.
Oh... and I wash my brushes every night... they stay much better under that wrap until I get them washed.