Not really. Just don't overdo it on a single request. I mean, the people doing cloning don't want to feel like they have to spend the entire day on your request. Common sense limits, not something set in stone. :)
I'd say don't do more than a half-dozen at a time. Or request something silly like two dozen clones. The guidelines in the topic post and follow-up kind of talk about this, I think. :)