20 hours, for example, would be enough? Not counting old content
Just teasing of course.
Playtime can be such a subjective thing too. Things like replaying, speed of reading, all kinds of things come into it. I've seen games talk about long play times but really it all comes from playing the same few hours several times to get all the ending, which is false content a lot of the time in AVNs because nothing substantial changes until the end. I have thousands of hours in CK 2 and 3 and EU4 and I have enjoyed almost every minute of it. But then other games I paid just as much for I only have like five-fifteen hours invested in them and got my full time and money's worth too.
Enjoyment with the game is more important than literal time spent with a game usually. I can play a game for a few hours, finish it, and have had a great time and never touch it again. Likewise, it is possible to invest many hours into a game and not enjoy it and leave frustrated without finishing it. I recently did this with an MMO my friend wanted to get me into. I played like six hours didn't have a good time and won't be going back. I'd have rather spend four or five hours with a game I enjoyed and finished all of it. Dark Souls has this effect on some people, it's a long game that many people leave unfinished out of frustrations even after trying to get into it for hours.
Still if that 20+ hour estimate is for real, I'm even more excited.