One other note on timeline… I've heard several authors whose writing I appreciate say that an author's note as to the timeline shouldn't be necessary. The fic should speak for itself and the timeline should be clear from what you've written. I agree completely. I'd just add that I think there's room for fics that have an ambiguous timeline. Not an ambiguous, confusing timeline due to poor writing, but an ambiguousness based on the idea that the moment being written about is timeless. For this ficlet the timeline isn't essential to the story. This moment could be happening three decades down the road if that's what makes the reader happy. It can be S2, S3, S4, or S5. Actually that's the point. It's something that happens all the time between Brian and Justin. It's just one little timeless snapshot of teh love.
100% yes to everything you said in that paragraph. Oh, I so wish some writers would give their readers enough credit to figure things out on their own. If the timeline is important and your story is well-written enough, we GET IT! If it's not essential to a story, we can always tell that as well and it fits seamlessly into the place we as readers need it to be.