Originally Posted by
Rayn3dr0p 
I think I interpret "once a cheater, always a cheater" differently from you. What this means to me is once someone cheats in a particular relationship, the precedent is set and the floodgates have been opened. In my opinion, that particular relationship is doomed. They did it once, and successfully if the betrayee stays in the relationship, so what is to stop them from doing it again?
My best friend (girl) had an affair a few years into her marriage, she was fairly young, had her reasons and made a mistake. They separated for a while, sorted things out and I know have been very happily married ever since. Married for 21 years and alcohol is NOT a factor.
My own AH had an email affair a few years ago, he stopped it dead as soon as I found out and with the recommendation of the marriage councilor, opened up (and was happy to) all his internet communication to me, to rebuild the trust.
In the early days I would check his emails now and again but as the trust built this would happen less and less.
However due to his alcoholism, he becomes very untrustworthy at times as he has lost all abilities to be reasonable and respectful to the marriage. Just checking the computer history recently, I have found he had been visiting porn sites and I have also caught him hiding smoking from me.
My alcoholic hides empty bottles around the place, hides his cigarettes from me and basically lives a paranoid, secret life. Any trust I have had for him has slowly dwindled and although with the help of Al anon and this site, I stopped checking on his beer supply (detaching), I am now back checking on his internet behavior.
I currently feel like a psycho, and I know this is no good for me, my marriage feels screwy, so I am once again, mentally preparing for the inevitable of going it alone.
I believe that cheating and alcoholism are two separate things and couples can overcome an affair if they both work hard at it and are able to move on. However a marriage in active alcoholism, its almost impossible.