Here's my 2 cents, based on my experience from several surgeries but specifically rotator cuff repair of full thickness tear and subsequent reattachment.
I came up with the notion that as long as I wasn't hurting myself, then I wasn't hurting myself. What I mean by that is, I let pain be my guide. During the rehabilitation/physical therapy period, I would slowly, carefully increase my weights, paying very close attention to how my shoulder felt during the exercise, and also how it felt the day(s) after. As long as all I had was normal muscle soreness and not "injury pain" (you train regularly, you know what I mean), then all was good.
I checked this theory with my surgeon, who agreed. He actually said that most people have no idea how to listen to their bodies, so for most folks he wouldn't think of agreeing to such an approach, but in my case that was an absolutely valid approach. Provided I was conservative, which I was.
Occasionally, I would push it too hard and would feel it the next day or two. When this happened I'd back the intensity down a notch and proceed more slowly.
It's been 6 or 7 years and have had nothing but steady improvement, no setbacks or "re-injuries".
So that's my suggestion to you. I don't think a specific time frame can be given as everybody heals differently. I think this is one of those things that has to be done entirely by feel. Followup MRI can probably gauge progress in black and white, but as for the progression, you're the only one who can feel your tricep.