I seem to remember a long thread about this a while ago.

I think there are many things to consider when deciding what's the best running dog. Such as: Is it likely to chase things? Will it kill them if it does? How muddy does it get? Will it overheat running in the UK? Can you control it easily with commands? Will it go insane if you don't run for a few days? etc.

I think we'll probably get another lab/collie when our trusty Max finally retires. Less fat than a lab, but less manic than a collie. Ours is now very good at ignoring sheep. He's in semi-retirement from running now (aged 10) but comes out for the occasional recovery run with me and Mrs Noel.

A friend has a Weimaraner, which can run all day. It's so strong she has a harness so the dog can pull her up hills. The weimaraner in question is very well trained, but I think they can be a bit daft.