Never used billboards, so I don't know much about it, but this sounds pretty annoying. Why not let users delete their billboards? "In case you want to use it again" is a ridiculous reason for not being allowed to remove them. Plenty of reasons why someone would want to delete a billboard. Just put up a clear disclaimer and confirmation page, then let users decide what they no longer need.
Good points here about Event stuff too. Between adblock and custom CSS, I don't see most billboard ads on Subeta, with the exception of Event button ones. I've tried to block them, but can't find a way to do it without potentially blocking more than intended. :( I wouldn't mind so much, but there are still KISS BUTTONS popping up long after Survival has ended!
I like 's idea of a cheaper, event specific billboard. Have an "Event" option for user ads that allows users to pay for their button to show up as long as the event runs.
Edit: I thought they'd finally all gone, but more than two weeks after I posted this, ANOTHER Survival Kiss button billboard pops up!
I'd love to be able to delete them too. I already accidentally added impressions to a billboard I don't use anymore instead of one I want to use because the images weren't showing properly. If I could get rid of all my old ones it would make things a lot neater
I have some old obsolete ones that I always worry I'll click instead of the one I want to use so this would be very helpful.
I love the billboard system but this would make it even better :D
Event specific ones that go out of rotation as the event is over would be spectacular.
I don't think editing would be a great idea - even though it sounds lovely the whole point of them needing to be approved is to be sure they are appropriate. If you can just edit things yourself that leaves loop holes that defeat the purpose of needing to get them checked.
Regarding concerns about editing billboards, what if there were functionality for a preview page?
You add in your images/links, text, and then when you submit it, it'll go to a preview page where you can check and make sure it's what you want. Then you can click for final submission, or go back and fix your work.
That way you could allow people the edit option while still ensuring billboard submissions are final.
Given the influx of kiss boards that are still floating around the site, nearly a month later, I think being able to pause and/or delete them would be ideal.

there is currently an option to pause them (it just relies on us remembering to go and do that), although if there was an option for a billboard to automatically pause at the end of an event, I'd be all for it! :D

If you were to edit an image to a new one that new image would have to be approved. I think having to pay CSC to submit a new image for an old billboard would be a good idea.
I wouldn't want an editing feature to let users create a new ad. So no changing of the URL.
I'd imagine this being used for situations where you've had a billboard on the site for years and feel like changing the image. Possibly because your graphic skills have increased. Or you think a new image would attract more people to your blog, etsy shop, ect.
The only time I've ever created a billboard was to get that one achievement for it lol. I haven't used it since then, so there's no reason for it to really exist anymore. Being able to just delete them would make sense.
But it seems like the whole system could use a bit of a revamp. Maybe being able to give a name to your billboards so you can more easily tell which one you want to use or add impressions to. And a way to upload a new image for an existing billboard would be cool also.
I know the holiday billboards can get annoying when the event isn't going on anymore, but that's more of an issue with people forgetting to go pause them or maybe forgetting that they even made a billboard to begin with. 10k billboards are pretty cheap now thanks to the bathhouse, so people probably end up with extra impressions that they don't use otherwise or end up forgetting about. Some way to automatically pause holiday-link billboards might be nice though, if possible. Maybe it could give you a sidebar alert/notice that your billboard has been paused because the event ended.