How many hours for an RPG?

Every so often I go back and play a retro RPG.  Not just SNES era stuff either, One of my favorites is Moraff's World, an MS-DOS game from 1991. It's wild to think that game and FF4 came out the same year. 

I noticed that I absolutely destroy these games now though. Like I went and played FF5 on the GBA version, Since I hadn't seen that bonus content. My memory from childhood is the game easily being a 60+ hour experience, but I blasted through it in half that time as an adult, even without playing it for a decade. But BG3? That soaked me for hundreds of hours, and it never felt like a slog.

The Asqueria demo is maybe an hour long, but it's just a demo.

So that made me think: What's the ideal length for an RPG with a balanced ratio of combat/story these days? 20, 30, 40 hours? More? Less?

Thoughts welcome, I'm curious.