While in theroy I agree with you, and only a few of my ewe lambs make the cut each year, then I cut again the next year-- or I did this until I down sized.Actually, I will have to respectfully disagree on this point. Raising lambs is just like raising chickens. Breed the hardy ones, cull twice as deep as you think you should, and then you are only perpetuating the best genetics. Some people breed everything they started the season with. Most people do this actually. And then they have no clue they are perpetuating problems. My healthiest lambs are born in deep snow and cold temps. I will not lamb past Feb. Hypothermia is not a problem if you have health and vigor. Having more than 400 lambs a year i can tell you that most people pamper and baby their lambs... use heat lamps... Or heaven forbid put them in an enclosed barn. This is a health nightmare waiting to happen and your survival will either be very low or it will be high only because you have lost sleep and a lot of time and money saving those who should not have been bred to begin with. If your average survival rate isn't over 96% unassisted, then your business plan and genetic knowledge needs assistance.
Breeding and livestock genetics are my business. If I were to treat it like a hobby it would stand no chance of providing a living. I run the entire farm alone and have no choice but to work smarter and not harder if it is to be profitable.
I am curious as to what your night time temps are in TN compared to mine in the NOrtheast. We might be talking rather different temperatures. IN the far north of VT, the one sheep breeder I know lambs in May. And one other I know here in Mass lambs in APril and in both cases the lambs are then raised on pasture. I suspect our temps are quite different.