How long? Until GOD SAYS OTHERWISE!!! I know it's not easy, believe me, I know.
But I don't think you can put limits on God by stating "He's had enough time - if He hasn't changed her heart by now, he never will", because you A. Don't know God's timing and B. cannot choose to live for God and for the flesh at the same time.
You're in a Flesh/Spirit battle right now. Your flesh, and the world, is telling you to divorce her and move on; find someone else who will respect you. But your spirit is telling you different, as obvious by your confusion and confession of love for her. The question is *NOT* "when is enough enough?", the question(s) is "Am I willing to commit to the covenant that I entered and lay all of this at the foot of the Cross? Am I willing to trust that God has this in control?"
If you cannot answer "yes" to the latter questions, then you may be in for a troublesome spiritual battle.
You asked "How in the world am I...". I believe that's the wrong question to ask - the world isn't going to help you at all, nor will it have the covenant of your marriage in mind. The world will say "you can't... and it doesn't matter anyway, because she's never coming back...". But what does God say?
The world is great at creating noise - the noise can be so loud that we often don't hear the soft spoken words of our Lord. We have to be diligent to listen carefully, consciously "tuning out" the words of the world and "tuning in" to the words of God. It's NOT easy - heck this morning I cried out "WHY!?!?!?" after just over 11 months of divorce because I had stopped tuning into the Words of God, which tell a completely different story.
I emplore you to check out
www.marriagehelponline.com. Order Erin and Dan's "Restoration" book and read it cover to cover, being sure to check each and every Scriptural reference as you do. It may not make the path you've been given to walk easier, but it will help you see the path itself.
When I was in a similar situation, everyone was telling me to move on, divorce her, kick her to the curb, whatever. I blamed her for everything. I thought to myself "I can never trust her again!" and "she doesn't deserve me!" It took a divorce for me to look in the mirror and see the scales fall from my eyes... *I* was the one who had done wrong in the marriage. *I* was the one who didn't love her as Christ loves the church. *I* was the one who broke our vows by not treating her the way Christ instructed. I've since learned that this divorce was NOT about what she did wrong or what she thought she wanted, it was about me... only me. I was supposed to be the spiritual leader who was to put his Marriage before everything but God Himself - *I* didn't do that, and everything fell apart. I do not blame her at all; in fact, I have the utmost respect for her and am very empathetic towards her pain.
The point is that it's time for you to look in the mirror and allow the scales to fall from your eyes... If you have a heart that says "she did this..." or "she did that...", your marriage is doomed before you even have an opportunity to save it. But if your heart is pure and humble before the Lord, with it's priorities in order, and beating with a love blessed by God, you will have an opportunity to change this situation for the better - to the benefit of your marriage, and more importantly, your walk with the Lord.
I've said it before, and I'll say it again (to myself moreso than you at this point)... When we request from God something that we desparately desire, all we have to give in return is our faith, our trust, our praise... and most importantly... our time.
Remember that fear, hopelessnes, confusion - none of that is from God. This is a spiritual war that you are in, and you are not only fighting for your marriage, you are fighting for your wife.
Head to your prayer closet - shut everything else out and focus on the soft voice of God... and let Him tell you what to do. If you listen to me, or anyone else, you will be listening to a human voice and ultimately the advice of a sinful person. God, and God alone must guide you through this, and I promise you that He indeed will. But you first have to put your faith in Him, your trust in Him... and stop putting time limits on Him. Remember Psalm 3 - lean not unto your own understanding. God is working here, let Him do so.
One peice of advice I would offer, that I believe is sound, is this: Walk in love around your wife. Wether that is on the phone, in person, over electronic means. Treat her with the love she deserves as a child of God. Renew your own mind in this manner, and I promise you that things will start to become clear.
Hang in there - KEEP PRAYING - and check out Erin's site...
bkg