Just came across a comment in march 2019 examiners report.
Basically there is a question asking about the advantages of DPP, the examiner commented that one of the advantage is that the DPP can assist in assessing sensitivity to a change in project life.
The report refers to DPB (not DPP) and does explain that it is the discounted payback period. I do explain what this is and the relevance of it in my free lectures (and in my free Paper MA lectures also because it is revision from Paper MA).