I'd finish the Elibe world before starting on Tellius.
Unless you have easier availability to FE6 than FE9 that is (so you'll be able to play FE6 at times you won't be able to play FE9)
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS







