It seems that your bosses working style is very inefficient. Some people have to demonstrate their importance by requiring changes, whatever you do. As a result, he takes maybe ten days of your working time to create one design that is used, when you could have created five different designs that are used in that time. BTW. You don't need a set of different designs - you need one good one.
I wonder what you mean by "boss" - is he the owner of the company, or is he your manager, responsible to others? If he is the owner of the company, it's his money that is wasted. He pays you a months salary for two designs that are used when he could get ten designs that are used for the same money. If he is a manager, he isn't wasting his money, but the company's money. At some point I think he would be asked why the work he is responsible for makes so little progress.
I'd say: One, don't worry about this. It's annoying, but only if you let it annoy you. So don't let it. You create designs, you get paid. Two, do not accept any criticism of your efficiency. Keep all the designs, keep all the different references, so that you can demonstrate that you did a good job. Three, do not under any circumstances accept requests for unpaid overtime. A boss who cannot make up his mind does not create a business need for overtime. Four, when raises are discussed don't accept anyone rating you down because of the small number of accepted designs. You must be rated based on the huge number of perfectly fine designs that you created.
All that said, at my place of work the designers are told for example "Easter is coming, we want some Easter themed design for a new campaign", and then some time later the designers come back with an Easter themed design. They know better than their boss how to create a design, and they know it. And the boss knows it.