I came across this article on Kim Lajoie’s blog about how song writers and producers sometimes want a longer song. This requires balancing material that is going to be interesting for a longer amount of time and a sound that matches. Producers have to be aware that attention spans for entertainment will often last no more than six minutes a song. Erick’s block Tarekith has great advice about creating mixes to dance music that will keep listeners entranced.
Good read:
What if I want to make a song longer?