Let me first say that as people waiting for the free gimmes of the result of your labour. You owe nothing to people who aren't even paying you for your game.
That said, I think the best way to keep people engaged for the wait would be a demo, it would also force you to perfect the starting segment of the game. Initial impressions in storytelling are very important and video games are no exception.
Length doesn't necessarily make a game better, but the impression i get is that this is an upgrade to Lux in every category, art, story, scope, game mechanics, etc. I can tell the Passion you put in your work from your other projects and i hope you do what makes you happy.
Yeah I'm not sure what the proper scheduling would be either, maybe around start of 2025 would be a good point to ask yourself where you want to end up. If your going to go for longer than shorter, it might be nice to release a demo.
I haven't tried GemCard, i'll make sure to do so.
Thank you for the Update.