Mine were tupped the last weekend in october and then left well alone as there was still plenty of grass left and they're in good condition.
January - started adding hay, topped up once per day
February - mid feb is 6 weeks to lambing, starting adding a handful of ewe nuts to introduce them & topped hay up twice a day
March - lambs due end of March, 4 weeks pre lambing consists of hay, concentrates twice a day and a lifeline bucket added.
They are due next week and have concentrates twice a day, hay checked 4-5 times a day and pretty much re-filled each time and a lifeline bucket ..... they all look fab.
So in answer to your question, ours get a 'maintenance' diet until 4 weeks pre-lambing. They are in good condition so feeding earlier than that just puts on weight whereas now their condition score hasn't changed so is being used on the growing lambs.