Glad you enjoy the game! =D
Current intention is to do 1 ecosystem every 3 months, and that will saturate my schedule. Plan is to have 10 major ecosystems with ~3 lesser ones (tutorial, town, ???). If the game does well, I have 3 others that could get added as an expansion.
With optimal work conditions, it takes approximately 1 month for lewds, 1 month for core gameplay (level design, env, combat animations, jewels), and 1 month for polishing (sound, bgm, bugfixing, testing, and all the bits and bops that I left behind, like tutorials, NPCs, dialogues etc... and adding new features).
It is my intention to add NG+ to the game, but it's not really a grinding game, nor is it meant to be infinitely replayed. Reaching 100% completion requires 5 play-throughs, and each one unlocks a special perk. of course they are cherries-on-top, not really "core" elements, but they will be pretty cool nonetheless.
I would expect this game to be as grindy as a souls-like. you can do it, but you are better off just progressing the game/git gud.
See you in the next update (early next week I'll be adding the Lamiacle boss fight) ;)