I find that if people like the song they will stay to listen to it, especially if the sequencing is also good. In many cases, it's not the length of the song but the song itself. I have seen many shows that play songs that while have a good beat for sequencing, kinda suck for Christmas songs. I stopped by one show back when I was in NJ and the songs being played were in most cases not even Christmas songs. I didn't even bother to stay to see all of the elements light up. There was another house down the street that was a bit smaller but was actually playing Christmas music, some traditional and others more modern and I stayed for the entire show, along with many others.
I think that it is more the song than the length of the song and the person creating the show needs to determine who the show is for. If it is for the creator of the show, then use the songs that you want and have fun with it. If it is for the neighborhood, then I would put in a mix and see which songs peopel stay the longest for and move the show to that style of music the following years. If you have 10 cars pull up, you are going to have 10 different tastes and opinions and there is little that you can do - short of a road block - to prevent drive-offs. If at the end you enjoy it and are proud of your accomplishments, then you win.