Mine was 8mths old when I inherited her from my uncle. She was 90% trained as a full worker and her mum was an Irish sheep dog champion. When I brought her home she refused to come into the house as she’d been made to sleep on a pallet in a barn. She’s 9yrs old now.
The herding /chasing instinct is just that. Pure instinct. You can try and train it out, but you’ll almost certainly fail – she will still attempt to round up anything fluffy. Non-compliance is not an option: you will get stalked, stood off and then nipped if necessary. I wouldn’t want to be a cat around her.
She was brought up in a farm with a small boy as company. She is utterly amazing now with my three: properly protective of the baby and great fun with the other two.
An old worker will be a loyal and calm companion in and around the home. They are properly grateful for the rest, like cuddles and a nice warm bed. A bath that doesn’t involve immersion in a 6’ deep tank and steak trimmings on a Friday night must be like dog heaven.