I'am in the habit of changing oil and filter every 5000km when I ride my Dyna 1340 on long trips, every 4000 on roads and towns.
I use Motul 20/50 or 15/50 semi synthetic special HD
Oils filters are very expensive and flow restritives. I have fitted a Billet oil cooler and a Golan oil filter and I clean it myself when I want...nice parts.
I can send you a picture if you want, but I think that you can find theses parts on the web (Parts and accessories various catalogs)