@niartchu The longest I've spent on a digital painting was a couple months, but I took pretty frequent breaks on it. Most of my detailed portraits take 4-8 hours and I'll take 20 minute breaks every hour of so.
@niartchu Something I've learned as an artist is that your style is constantly changing. The best way to find your style is to draw consistently and don't shy away from details in your art that look different from other peoples. Do what comes naturally first, and then look to improve it.