She has been cheating your entire marriage so to put the past behind you would be to ignore that she has a different view of marriage than you. Her track record would guarantee the same. She knows you stay no matter what she does.
I left to save my future, my self respect, and to possibly to find someone who values me and shares the same belief on how a marriage should be.
We are the same age and it is hard to start again, but you have given forgiveness over and over and at some point you have to put yourself first. We can't fix what is wrong with them, we can't love them into faithfulness, we can't fill the void that makes them run into the arms of other broken people. All we can do if make sure they do not destroy us.
Don't leave to see what else is out there, leave to find yourself. You will probably realize that you have neglected you all these years to prop up her insecurities. Mine looked and acted confident, but was insecure and what I thought was strength most people saw arrogance.