According to this
http://www.yvr.ca/en/navigating-YVR/...rotection.aspx US CBP is operational between the hours of 4:00 AM - 8:30 PM. Passengers who are departing on flights outside of this time should contact their airline for more check-in information.
Do we have the option to check in early for our flight at 22:55? After reading how long US CBP can take in IAH, I would really prefer to do these formalities here. We don't mind checking in early to catch them before they go home for the day.