Writing the script for The Fragmented Dream (also long af), from start to finish, took a year and a half. I wasn't planning to take this long, but got pretty bad writer's block around the middle. It still needs heavy editing, though, so I guess my work with it will be never truly done...
Before I began writing the script, I spent another year and a half outlining it, planning the story, etc. (To be fair, it's been in slow development for a much longer time, but it was around that point, four years ago from now, that I decided to make it what it is now.)
So yeah it's been a slow process but I don't regret it (though, I do wish it was a bit faster...) - I'm very much a planner, I need to have things planned out as much as possible before I even begin. I'll never be one of those creators who are able to write as they go
As for drawing... yeah... maybe it will be completed in this century... I technically started in late August of 2018. I still haven't finished the first chapter, planned to be ~55 pages long. RIP me