There seems to be an ebb and flow as to what they are most concerned about at the border. Remember to have the vehicle insurance information and cab card available, as they can stop you from crossing if you don't have them if you are asked. We once crossed at 4:00am, primarily to beat the lines at the border for opening fishing season. That was a mistake, because the Canadian customs/border guys were bored and spent 1 1/2 hours doing everything but strip searching us. This was for a group that does this 3-4 times a year for going on 30 years, so it's not like we raised any red flags.