Learning and Tempo

Ken Perlman's Clawhammer Style Banjo introduces a concept then a tune that uses it, then it introduces the next concept and a tune that uses it, etc. I really like this approach.

When going through the book should I learn each tune so I can play it cleanly at slow speed (e.g. 80 BPM) and move on, expecting that speed will come later?

Or should I remain on that song until I can get to 110-120 BPM before moving on?

What is the better approach to learning?

Thanks!