Woodchuck a collar is as important as the two of you want it to be. For most people they represent a commitment between two people to the relationship and serve as an outward sign of the BDSM aspects of the relationship.
The eternity collars are very nice and simple, their sublule design allows them to be worn 24/7 with out calling too much attention, but are recognized easily by those in the lifestyle.
Good Luck with your journy.