I'm not sure if this was mentioned to you before, but after you watch Season 4, that is the end of the Fox era as it was cancelled by them following that season's finale.
Season 5 constitutes four direct-to-DVD films, but each film was chopped up into 4 TV episodes eacah as well so they could air on Comedy Central (who gained the rights and resurrected Futurama).
To save some time, you could watch each of those films in their entirety, instead of one episode per week. Would take you 4 weeks to watch Season 5 instead of 16!
