Did my mechanic suggest a new part prematurely?

my mechanic had me replace my fuel injection regulator because my cylinders were fuel rich. Now they are fuel lean, and he is inspecting the injectors. Shouldn't he have done this in the first place? He says there was no reason to check them because they haven't had problems starting the car cold, but I have told him a few times that I have problems starting the car at all, especially when it is cold. Regardless of what anyone says, i will pay him, and I understand human error, etc. Please let me know what you think!