At the moment I paint the same motif in two formats simultaneously.
I use the same color palette to save a lot of mixing time. So I have more time to focus on brushwork for example. And when I learn something at one painting I can use this knowledge directly on the other painting.
The composition will be changed slightly to keep me excited.
Also I will vary my brush making. One painting will be tighter, the other more gestural.
Give it a try. You can also try the paint completely different subjects with the same palette or paint the same subject with different color palettes.