Why are my notification icon customizations lost after six months of disuse?

A customer had a notification icon that was used only once every few months. They found that even though the user configured the icon to appear on the taskbar, if six months went by without the icon being used, then its configuration disappeared from the taskbar notification configuration control panel, and the next time the icon appeared, it received default treatment instead of the customized settings. Why is that?

An application can create and remove taskbar notification icons by calling Shell_Notify­Icon. When the application removes its taskbar notification icon, there is now an open question: Is it gone temporarily, or is it gone for good? There’s no way for a program to say, “Hey, I’m removing this icon, and it’s never coming back.” (For one thing, it won’t be able to say this during uninstall, because the user doing the uninstall cannot send information to other users whose profiles might not even exist on the local system.)

The notification area uses the heuristic that an icon that hasn’t appeared in six months is probably not coming back. Or at least if it does, you won’t mind re-customizing it.

But it means that if you have a notification that occurs, say, only once a year, the customization will be forgotten by the time it comes back around.