I have 4 cade lambs. Youngest born here and abandoned is 6 weeks, then 2 runty rescues about 8 weeks and a rescued crow pecked (one eye, part ear and partial loss of tongue) about 12-14 weeks old (dudlea).
At what age do you think they'd be OK in a field overnight without adult sheep? At the moment they have a pen in the barn overnight but dudlea can hop out of that section and plays around in all the stuff stored there.
Predators are the obvious concern. The field is safe from the viewpoint of lamb escape. They go there daytime at the moment.