Great thread RHW I was thinking about this just the other day. I'm to the point where I "almost" totally trust J again. I don't think about checking up on him and don't worry that he'll cheat. We had an incident last month that concerned me, but I noticed that I've stopped assuming that he's probably thinking about another woman.
My how long is about like what you said - Until the R was fixed and solid again. Lots of time helps, but it's been since I've become sure of J's love and committment that I've been able to totally trust him again. He had an A years ago before the lastest bomb. I didn't trust him after that and I can now see it was because I knew our R was not right where it should be. I know he cares. I can see it in his actions and his eyes.
You're right, it's definately a choice to forgive, and trust again. If the WAS is transparent and totally committed to working things out, he/she will be patient while we recover and regain trust. That's another reason I've found trust again. J worked through the issues with me. He talked to me and understood my feelings. He comforted me and just listened. When he dropped his defenses and the secrets were no longer secrets, I was able to relax, trust and heal again.