DPC's comments on the length of the game haven't changed much: 10-20 episodes. That's a very wide range, but it's been consistently wide.
As for opening up other paths, that's the way the game reads to me. In Episode 5 we explicitly identify her relationship with Chad as why we turned down Sage. That makes it an obvious topic to revisit if she ever broke up with Chad, and sure enough the end of Episode 5 makes it clear that WILL happen (if we hadn't already guessed). Likewise Episode 5 specifically asks if the MC still has feelings for Maya or Josy after rejecting the thruple path (and remembers the answer); again, the implication is clear.
Given that Jill and Bella were still in the pre-path stages then, it's hardly unexpected that decisions for the other 3 LIs might not yet be set in stone. That tracks well with decisions earlier in the game. We can start the fuck buddy path with Sage by fooling around with her in either Episode 2 or 3. We can initial the thruple by sleeping with either Josy or Maya prior to Episode 4. And we can have sex with Sage in Episode 4 whether we chose to stay with her or not. The game has illustrated there were multiple ways to progress with a LI prior to Episode 7.
On the question of whether giving a Sage path for those who turned down being her fuck buddy is fair, two points. First, DPC made it abundantly clear with Acting Lessons that he's not particularly interested in being "fair" nor is he worried about pissing people off. So while we can certainly discuss the matter it's hardly an obstacle to how BaDIK will act.
Secondly, I find the notion that fuck buddies "earned" a special status with Sage misguided. If you chose to start an affair with someone in a formal relationship you shouldn't expect that affair to be the one true path to love. If anything, you should probably expect that the resulting affair to a be very short-term: full of passion that burns out quickly. Giving the affair a legitimate chance for more is already being generous IMHO, even if it is likely a necessary concession to AVN tropes.
At any rate, the point is that just because there are two paths to Sage (regardless of exactly which ending(s) each path gets), that doesn't make it unfair to the path that opened first. The journey matters at least as much as the destination, and in this case the fuck buddy path has a very different journey prior to Episode 7.
Now I agree, it will be a waste to conflate the routes going forward, but I can't rail against DPC for something he hasn't actually done yet.
We don't know how old the relationship between Sage and Chad was. In the Episode 5 flashback (~two years before the start of the game) , they don't seem to be an item yet (though Sage is obviously enamored with Chad). When we first see them in Episode 1, their relationship seems to be well established. That suggests we're looking at a relationship between .25-1.75 years old, give or take.
Anything up to a year seems plausible to me; if Sage was truly smitten, she'd be willing to wait for Chad to be comfortable. Longer than that is still not completely outrageous (Sage is pretty clearly frustrated, after all), but it does start to undercut her comment in Episode 5 that guys don't normally reject her.
There's also the possibility that Chad DID have some sexy times with Sage on occasion, at least early on in the relationship. It's less likely now that we know Chad is gay, but we still can't rule it out.
