I have always saved files down to the previous file format. When the format changed in 2018, I still saved in 2013 format. Since moving to 2020, my pipe drawings, both my models and files I data ref them into will not save down to 2013. What's funny is that I can open the dwg in 2018 and save it to 2013 format. I have no issue saving in 2018 format, but I share files with other consultants and they may not be running 2018 or newer yet.

So for best practices, when do people normally move to the latest dwg format?