Totally depends on: when they were born, breed, type of grass you've got, upbringing until now, weather conditions from now until slaughter etc etc.
My lambs are hand reared, born in Feb/early March and will go off from August right through to end of October, they are fed hard feed every other day more to keep them tame but it does benefit them. Our grass is very good though, well fertilised and rotated so they finish very well on mostly grass alone.
I would get 3 lambs though they are better in numbers and 2 could cause issues if 1 died.