I'm not 100% sure on this. It used to be the case. Now the My Gallery page states:
That might be the case since eBid starting storing images in the cloud rather than on their own servers and space/cost became less of an issue to holding on to images.
The help page,
https://www.ebid.net/uk/help/selling-on-ebid#faq-13, still refers to the 10 days. Though eBid do not have a good history of updating help pages to reflect changes to the site.
If you find the images remain after the 10 days maybe you could nudge admin to update the help text.