Hi Steve,Thought I'd stick my 2 cents in here since I've been replacing banjo heads for people for the last 40 years or so; some of them on instruments I made. When real skin was the standard and one could find well made heads, the pros usually needed a new head every 6 months or so. Since skin is so affected by changes in humidity, pros who needed their instruments to always sound good had to adjust the tension frequently and usually broke about 2 a year. The rest of us got by on many fewer changes. The bench mark of what sounds good is still the most important measure and using a torque wrench has LOTS of pitfalls. Even a small burr in the threads will affect the torque need on that particular hook. Are you lubricating clean threads or tightening older, dry, corroded ones? That'll change the torque readings 400% or more. Overtighteneng one hook will cause the two neighboring hooks to loosten. The quick route to breaking a new head is to tighten the neighbors in stead of loostening the overly tight one. Also, some instruments need tighter or looser heads than others to sound best. I could go on here but you get the point. If you like the sound, it's the right tension.
Best, Ray Frank