My program is a bit different than many mentioned on here, it seems, in that our practicum placements aren't generally procured by any type of official means. We basically let our advisor know where we'd like to get some experience, and then we contact that site supervisor to see if they'd be willing to take on a student.
That being said, I've completed multiple two-year placements, yes. However, I should also mention that during those years, I was working at multiple sites (two to three) so as not to restrict the variety of my training experiences. So long as you could do something similar, I'd imagine taking a two-year placement would be fine.