Another time factor is output: proofing and printing. That is, getting your work out of the computer and onto paper and having it satisfy you. It can be time consuming and expensive.
The key is in remaining just aloof enough from a painting so that you know when to stop.
Sixteen million colors in your palette are hard for any artist, especially a beginner, to turn down.
The artistic process in digital art is very much the same as for making other kinds of paintings.
Once an artist explores the vast variety of tools and features available on the great programs, we're hooked.