“Producing repetitions was part of the nineteenth-century academic tradition. Most prestigious was the artist’s repetition of his own work, which was held in equal esteem to the first version.
“A r?petition of this kind was considered to be an original and autonomous work. A repetition on a smaller scale than the first work was referred to as a r?duction.
“…Van Gogh set out in works like [his sunflower paintings] to improve a favourite subject .”
— Marije Vellekoop in Van Gogh at Work, page 191
When you’ve finished a painting, take all the “what if I” and “maybe I should” thoughts and apply them to a new canvas. Do another version of the painting, aiming not for an identical twin but a sibling, similar but not exact. It helps you develop ideas further, see what results if you do try something you didn’t before for whatever reason, gets things out of your system for better or worse.
IMHO there are several reasons to repeat your own works. One of them to master technique and to remember how to-s of successful picture.
Another more common reason to repeat the sold pictures. For example I made 4 post-sale repetitions of my 3-leg camel. http://natalyakalugina.in.gallerix.ru/expo/fauna/vesennij-prizyv/
Another reason to repeat a prototype work is to make a picture meeting the size requirements of the commission.
As for me, I find repetitions bo-o-o-ring. They look sometime more “up- to- the- rules” but less emotional and sincere. Amazing that repeation takes more time to finish then prototype.