2005-10-01 : The effect has no stated duration, so a land turned into a creature this way continues being a creature as long as the land is on the battlefield.

2008-08-01 : A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn’t matter how long the permanent has been a creature.