If you don't need to crimp bullets, is there any reason not to have the chamber cut allowing for a neck length about 1/10 inch too long? It seems to me one wouldn't have to bother with trimming cases.

One concern I can see is that as the neck grows longer so will the bullet pull. This could raise pressure and velocity slightly as the cases stretch.

You can have the nack cut as long as you want as long as the smith has a reamer with the dimantions that you want.
One big reason to trim cases is not to make them fit, but to keep them equal length, possibly a factor to consider in evaluating accuracy.

One problem with a chamber neck which is too long in relation to the brass is there is a tendency to build up hard carbon fouling in that area ahead of the case. When this builds up at the beginning of the throat it can hurt accuracy and is hard to remove. Regards, Bill.

You don't need a special reamer to cut a long neck. A stqndard reamer will cut the body, neck and throat to standard specs. If you want a longer neck, use a neck reamer; if you want a longer throat, use a throater; if you want a longer neck and thoat, use a neck and throat reamer.

Usually you don't mess with the length of the neck portion. You may want to alter the diameter of the neck or lengthen the throat for whatever reason.

Jim