If you take as the definition the one that is negotiated at the OECD, on average, it would be about once every three years, when the OECD reconvenes.
At an earlier point in my career I participated and contributed to an OECD working group on conflict, peace, and development, which brought forward a series of important guidelines to help guide donor activity and aid activity in conflict situations. That has since been translated by the statistics committee into changing and widening the number of activities that donors can count as ODA. Most of the growth in that area has been due to changing forms of peace and security-related assistance. It is certainly not everything that governments do in terms of promoting peace and security. I gave the example of the African youth force that is counted as ODA. The line is drawn. It's a negotiated line, but it's definitely been widening in the last ten years.