That's just my opinion, I figure most people who are interested will bid within a day, extending it to a week just has you playing the waiting game, and that's no fun lol
Also I seen you had the minimum bid start off at 50, I would say lower it a bit, but seeing as its already a success, keep it as it is haha. Just something to think about in the future
3-5 days is generally a good length to set for it. This gives people who don't get on every single day a chance to see and bid on things. Most of your highest bidding will come within 2-3 days though. People are generally quick to drive a price up and then it just dies, with one person holding the high bid until the time is up.
For a single character YCH, yes. More character slots that are available should have a longer availability though. Like an orgy with four characers should go maybe a week or so, just so plenty of people have time to bid. Someone really wanted slot A but got outbid, they may try for B instead or something. But yes, 3 days is a good starting point, with most of your highest bids coming in on day two.
You may also consider an option to prevent bid sniping. Someone puts in a bid a day before the auction ends..then someone else puts one in a minute before it ends to guarantee their win. Kinda upsets people. Extending the auction by an 15 minutes to an hour for a snipe helps to even things like that out. It can also renew interest in a piece and drive the price higher.
You might also consider setting a base price and a minimum increment increase price. Perhaps even teirs of rewards depending on the picture.
For example, you create a new YCH. The bidding starts at $20. Minimum that people can increase that by is $5 (so it goes 20, 25, 30, 35, 40, etc.) Say at $20 it starts as a sketch. At 30, line art. 40, flats with some soft shading and maybe a single colour background. Then, by the price of whatever a normal commission from you is, offer the full package. Full colors, shading and background.
You may also consider an option to prevent bid sniping. Someone puts in a bid a day before the auction ends..then someone else puts one in a minute before it ends to guarantee their win. Kinda upsets people. Extending the auction by an 15 minutes to an hour for a snipe helps to even things like that out. It can also renew interest in a piece and drive the price higher.
For example, you create a new YCH. The bidding starts at $20. Minimum that people can increase that by is $5 (so it goes 20, 25, 30, 35, 40, etc.) Say at $20 it starts as a sketch. At 30, line art. 40, flats with some soft shading and maybe a single colour background. Then, by the price of whatever a normal commission from you is, offer the full package. Full colors, shading and background.