Gilman Louie showed the way ahead with his very sucessful Falcon3.
The base sim was followed by Mig-29 and F-18 addons and additional campaign locations. Each spread the work load and maintained sales of the base sim well past the normal first wave.
The addons had the cash flow equivalent of a new sim going out the door every six months. That suported and maintained an enthusiastic team for several years.
The same was intended with Falcon4 but we can see the result when Gilman sold and the new management abandoned the base strategy.