How open can an open adoption get?

We have a very open adoption with DS's BM with contact. She'll invite us to family events so her extended family gets to see DS. They had a birthday party for him this past year. She came to his one year birthday party with our family. We feel very blessed to have her as the BM of our son and hope that we will be able to have a similar relationship with the parent(s) of our future child(ren). It really varies person to person though.