General best practice is to (a) upstream as much as you can, and (b) keep as close to -HEAD (the development branch) as possible. Some discussion on this at the Vendor Conference from a few months ago:
* https://freebsdfoundation.org/news-and-events/event-calendar...
* https://www.youtube.com/playlist?list=PLugwS7L7NMXzSalaF4l_7...
Basically: if it's not part of your secret sauce, upstream it.