I have things that I can confidently call conworlds going back to my middle school days in the late 90s.
My current Lonely Galaxy setting is a rework of an earlier project I called variously The Last Grand Adventure or En after the in-universe name of the world. It has roots going back to my freshman year of college in the early 2000s.
I conworld mainly as a means of escapism. My current conworld was born out of a time of extreme stress. I couldn’t handle the real world, so I retreated into my own. Perhaps not the most healthy way to cope, but eh.
Not long. I’ve been interested in it for years, but never wrote anything myself until less than 2 years ago when i started my current big project.
My love of some of the works that have inspired my stuff is much older, of course. I grew up on J. R. R. Tolkien and Douglas Adams, and various fairy tales and novels i only vaguely remember now.