He is my only friend to be honest and not speaking to him would mean not speaking to anybody.
This, combined with the other details you gave of how he's justifying his affair (talk of "needs" and dangling the prospect of coming back to you), worries me, Bat. This will sound harsh, but I worry that your relationship wasn't on sound footing to begin because you didn't have your own life independent of him, making you very isolated and vulnerable to manipulation.
Now that you have time to yourself, I really encourage you to start building your own circle of friends and finding out who you are outside of a relationship.
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I know this is a stupid question but do you think the A will last months or even years?
I've read in several places that most affairs die within 2 years, the majority ending within 6-9 months. A very small percentage of affairs turn into marriages, and most of those marriages fail. I understand why you ask this question—you want to have a timeline for when H might return. I understand seeking hope from this information. But really try to live your own life, keep moving forward instead of waiting around for him.