However, if I was to play it safe, I'd say this. If you're bulk building links, keep the volume steady. If you're building them by hand, one at a time, I wouldn't expect any issue.
I build links in bursts. I buil a calculator or something, then build links like crazy. Then nothing. Then I get an idea and off I go building links again 3 or 4 months later. But since they're all one up, 'building links' for me might be in the 10's at a time.
Automate link building doing something like directory submission might be a bit different.
I've built links for clients that have tens of thousands of links and some who have started with (literally) zero. My only rule is to diversify the links as much as possible to limit the liability. Also try to build links that not only build PR but also traffic: Link traffic always converts better than SERPs traffic in my experience.