Most took 5-10 hours, but the photo of the couple covered in black spots took about 15 hours. That one was a woman's only surviving photo of her parents, so she was extremely happy with the results. I did them all for Reddit users for free, and it was very gratifying. I'd recommend fielding Reddit requests as a good way to practice. Here's one I worked on for two days before giving up, early in my stint doing restorations. https://imgur.com/a/56pSsS7 I really should start over, but don't have the drive anymore. I'd say that was my most ambitious attempt. The guy I did it for still had it framed, despite its flaws. Thanks for liking my work!