Beyond co-sponsorship of the SEI, ARLIS/NA and VRA have held their conferences together
from time to time, and this 2005 email (RIGHT) documents the consideration of a joint conference for 2008. Apparently, however, that joint conference did not take place. According the VRA Web site, although ARLIS and VRA had shared a conference earlier in the decade, the organizations did not hold a joint conference again until 2011.* Since that time, however, the ARLIS/NA-VRA Joint Conference Task Force has made progress in ensuring more shared conferences will be held in the future.
*http://membership.vraweb.org/organization/committees/vra-arlis/index.html