[@Rune_Alchemist] oh, Slash already asked me in a PM. He was curious about how many years you could stay at BUM. The answer is [i]technically[/i] unending. You graduate once you become Master ranked, and ranking has no bearing on age or year. So unless you drop out it's entirely feasible for a "student" to be in their late forties . . . 

[@Riffus Maximus] Sadly there aren't any teacher spots open :( You could play as a student on the verge of Masterhood (graduation) however.