This may just be the most useless tip you'll ever hear, but I saw it and thought I'd pass it on.
To save the oil paint on your palette at the end of your painting session, you can submerge it in water. Just scoop it onto a piece of plastic, glass, jar lid, and put into a container with water over it.
I've had some cad yellow submerged for 4 days now and it seems the same as usual. Not sure how long it can stay like that...
Probably not something you'll use every time but one for that special mix you happen upon.