I bring a G22 and my 9mm CZ to the range with me about once a week. I know exactly what you are talking about.
I think the snapiness of the .40 may cause more flinching than other calibers and requires a bit more discipline to overcome and shoot well. As you mention, snap caps at the range are great for that. But, if you don't fire the .40 frequently enough, I think you can lose that level of focus required to shoot it well.