In my opinion and experience, sizing bottle neck rifle cases can be one of the most confusing aspects of reloading. For the purpose of this post, I'd like to make a distinction between fulling sizing and bumping the shoulder back. This discussion applies only to bolt rifles.
I personally stop neck sizing years ago after encountering chambering problems in the field, the occurrence of which was unpredictable. As you stated, one can check chambering, but this becomes tedious and, in my opinion, best avoided. The issue then becomes how do you size the case to provide for reliable chambering without having to check each round plus avoiding oversizing.
I adopted the approach of full-length sizing cases all the time. As you're probably aware, full sizing also sizes the radial portion of the case. In my experience, it's the radial expansion that leads to a lot of chambering problems. One can often go many firing cycles without the case lengthening to a point that creates a chambering problem. Therefore, I basically agree in principle with your position about bumping the shoulder only when necessary or stated another way, only the amount needed to prevent over working the case or creating excessive case headspace.
Depending on the rifle, I set the FL size to produce the minimum amount of shoulder set back without extruding, lengthening the case. I have some rifle with custom barrels that work fine with a FL case that has no set back to .001". As cases age without annealing and hardening, some adjustment becomes necessary. This where I found that Skip's Shims to be useful to make easy changes in the amount of sizing.
Bottom Line: I believe FL is very beneficial to reliable chambering, but shoulder bumping needs to be used judicially and not blindly. By monitoring the fire case headspace one can set the FL size to provide an optimum amount of shoulder setback for a specific rifle.
