My personal opinion.....just the way I think....is that if you have plenty of parking space that you want the customer to see cars in the parking lot and know that there are people there, however long lines visible can discourage people. If you're near other haunted houses and they can see the long line from the road, they may just skip over yours because they don't want to wait. However if they drive by and nobody is there at all....they may keep going as well. I have pulled up to other houses before and been the only car in the parking lot and all of the actors go running back inside......we didn't stay. I guess its just all up to personal preference, but if you can get them through quick like a group of 8 every 2 minutes or so that would make for 240 an hour which should make for small lines if you get them through fast enough.