I also find that hc shouldnt be played each update. Frankly thats the cost of slower burns and also why you dont get that many of them. People want content NOW. If an update isnt steamy and progresses enough, people feel CHEATED. Because they waited for the update with bated breath and brought it up in their mind. Its a need to fast gratification.
I think thats why some of the best slow burns come from japanese devs, because their development is different. They dont do update per update, they release the full game as is, maybe with a demo before. That way people dont keep pestering the dev for faster progression and end up ruining the game flow.
That being said, as I mentioned. 2 heroines is best, 3 max if you are a good writer. All henterias kinda fall into this trap of giving too many heroines, though I feel with the last one the dev got it the "best" out of all their games. Still would prefer 2 heroines and perhaps more games.
If you imagine each update that went into a side girl would have gone to 2 main heroines, the game would be done already. You would still have the slow burn, but it wouldnt drag so much for a lot of people. Then you could move on to a new game so it starts feeling fresh. Also perhaps try to break the grope, handjob, blowjob, thighjob, sex, anal, group sex progression that has become pretty set in. But that is a whole porn game genre problem and I am not sure what the answer is, without putting down the pedal. I guess the way of ntrpg 2 and the game I keep blanking on (red haired tomboy, dev had 48 in his name I think?) where they had a loong setup without any lewd stuff, and then hit it to 100 suddenly.
I think at this point ntaii is pretty settled in and is afraid of making any drastic changes in their style, which I understand. If its your livelihood, you are afraid to rock the boat from something that works. I guess thats why whole AAA gaming has gotten so stale, its more predictable and cozy to be "safe", until you reach a point where that in itself becomes such a problem that it no longer is.