The only time to even consider it is if the reasons for you breaking up is gone.
If it's something like she drives you nuts, vice a versa, or some other compatibility reasons probably not a good idea.
In some situations its a case of one partner not ready to make a commitment of any kind and the other partner is. If this time around both partners are ready to make a commitment it may be worth a shot.
The important question to ask yourself is; If I do this, will the problems we had before just pop up again?
Geez I sound like some radio advice show guy. Anyways you get the idea.
