If you're really serious about doing this (I'd advise against it, but I don't know your reasons or your circumstances):
If they don't believe you're 'truly' repentant, they won't reinstate you. It's that simple. It all boils down to their perceptions of you and whether or not any of those elders have an ax to grind with you. Put on a sad face, eyes downcast, maybe squeeze out a tear or two. Agree with whatever the elders say. Holy Spirit has nothing to do with the process.
As far as I know, there's no mandatory minimum time you have to serve as DF'd before you can be reinstated. I've heard of some being reinstated after only a few months while others have waited two or three years for reinstatement. Elders have pretty wide leeway in whatever decisions they make and you have no right to question them.