Traveling with roof vents open...good or bad idea?

I open mine while traveling, but in storage/not in use, I close it. To go one step further....when doing a long road trip in the summer months, the last 2 hours or so of the trip I will slide open 1-2 windows prior to arriving at our destination. Unless of course it's raining. It always helps with cooling the travel trailer down 5-8 degrees. I have done this for years with no issues.