It might go a little faster for you if you breed for one. And it could go even faster yet if you do the breeding in Emerald with a Pokemon in your team that has the "magma body" ability! :D (Magma body lets you hatch eggs in half the time, but it only works like that in Emerald. ) Anyway, good luck on your bagon! I hope you get it!
Edit: I was wrong about what that ability's called. It's called "Flame Body." And in case you were wondering (as I know at least one of you were) these pokemon can have it: Magmar, Magby, Slugma, and Magcargo.