Zero or one.
Repeated sign-in requests might indicate a problem with your browser not properly retaining or updating cookies, a blocked or corrupt eBay cookie, or a network issue if you are using a hotspot or a VPN or certain kinds of privacy software.
Some users seem to be having a problem specifically when adding an item to a Watch List, lately. Switching to another browser or using a private or incognito browser window seems to help many of those.
