Only once in my 25+ years of hunting have I needed a second shot. It was on a spinded deer. I will add, it was with a ML using a slip fit conical and put her down quickly with a second shot. No fuss, no problem.
That being said, while thinking of a need for a quick second shot does enter my mind for planning. I do not have any load with any of my MLs that can't be reloaded on a dirty barrel with the same bullet I am using for the first shot. So for me, it's a non-issue.