A collage might take me several days, like this one
Or a matter of hours, like this one
In other words, when I paint, I can't stop until it's finished. All I need is a paintbrush, and paint of course. With collage, I go back and forth; there are so many more elements involved and I need time to decide on composition before I glue anything down.
Simplicity is the removal of the useless and the unnecessary--source unknown