Yeah, the motivation you may have for your games is perfectly valid. I was just telling what i do.
It's okay if you have a story, lore, fictional universe, etc that you wanna develop and evolve and make it bigger as you say.
I was just telling that i do after ending a project is rest a bit. A week, two or a month (depending how i feel). Brain is like a muscle, you don't want to make it 'weak' or 'sore' (like mine XD) but if you keep doing effort it may broke.
The feeling of wanting things bigger, famous, polished, etc is a trap sometimes. Rest is also part of the developing process. It's a time where the brain recovers and you can use to... idk, watch a movie, read a comic, make a trip,etc. Things that may give you ideas for your main project and making it grow.