Interesting angle, as I'm probably the opposite on the 'done' aspect for client work. I mean, at some point, I stop, but usually want to keep iterating on things for the client when they simply don't want to. They don't have the bandwidth for continual iteration - they need something that works for needs X, Y and Z. Once it meets those needs, they're 'done' (and usually 'done' with me too). I struggle to not keep working on something, iterating, etc beyond what the initial specs were.

I'm working with a couple clients where it's an interesting mix - we're iterating the product to meet evolving needs, and discovering some of those needs as we go along, but many projects aren't like that.