Unfortunately, I can not give a good reference but here is a procedure I have read about that may solve your longevity problem.
I was going to try this, but then started firing my SMLE's less frequently.
- Put an "O" ring around the case just above the rim for the first firing. This makes sure that there is no gap between the bolt head and case; therefore, no stretching. The shoulder moves up.
- Segregate used cases by rifle. Removes problems with different head spaces and chamber depth from the equation.
- Then neck size. These custom made cases, for the rifle, now effectively head space on the shoulder like rimless cases and last a long time.