We typically pause other work and, as a team, pour all of our focus and resources into one client for eight hours straight. Thus far, this collective effort has quickly revealed itself as successful and most certainly worth the resources.
SEO agency Distilled has a neat thing going here. Their hack days are a really creative way of getting a lot of work done in a short amount of time. I’ve been a fan of group sessions since college (booyah, meeting rooms!), which were a lot like this — junk food included.