I almost always go on photographic excursions with another photographer. I do this for two reasons, 1)safety - in case one of us has an accident or we are in a dangerous area, and 2) we feed off each others ideas.
This said, once on location we generally are some distance apart, up to perhaps a mile, so that we are working independently, but once again share ideas when we are back together.
Obviously I am selective as to whom I choose to go with.