Huge advantage to all day impound and early morning return runs: You never have to set up a pit. Be ready to make the first half of the record, straight from first inspection. Bike goes to impound until morning. Go straight back to impound and then make your class change....and so on until you made the records you came for. It is a lot less stress and saves money and time.
Also...the guests and spectators love dropping by impound to see what is happening and who is in there. It is very nice for those visitors and it makes the event feel "organized" for their enjoyment (after all.....they do pay to be there and they should enjoy the show!)
As far as what to call the record, I always called it a "Bonneville record". That's about all you can call it, considering all the possible events down through the years.