2 months
Is it hard to beat? Yeah, kinda if it’s not your thing. But I had a lot of fun with each reset, because of all of the little subplots and character moments back at home base so I was never too disappointed when a run ended prematurely. I can tell you it took me way more than 30 attempts!
This is how I feel. And honestly how the developers of BG3 seemed to feel. Additional context for other readers if not necessarily for you, but 3.5 and Pathfinder have a lot of what they call the “magical Christmas Tree effect” where someone using Detect Magic on a player character would see a magical aura around every single one of your body parts. Barring specific character build decisions there was usually a best-in-slot magical item for every place you could have one, and the difficulty curve of the game assumed that you would.
5e, especially early 5e, attempted to curb this. Magic items were rare and powerful, but more importantly interesting. Strict numerical bonuses were powerful but boring so they were mostly eliminated. Flash or nothing was the name of the game, and indeed some magical items literally do nothing but enhance looks.
BG3 said no to this. Many possible character builds can only be done, or are strongly encouraged, with sets of magic items. It was an attempt to add depth and choice back in while restricted by a system that had little of it.