I am adding a entry to the registry like so:

Zend_Registry::set('EditMode',1);

I am doing this in the init() method of the controller if the user has pressed an Edit button.

In my models I do:

if(Zend_Registry::isRegistered('EditMode'))
{
.... do edit stuff
}

Here is the problem: Immediately after the user presses the edit button and the flag is set in the registry, in the controller all works as expected. If however another submit is performed after EditMode has been set the Zend_Registry::isRegistered() call returns false.

How can the entry go away?

Hi, I'm not sure I understand you right, but Zend_Registry is something instead global variables, not to save persistent data (e.g. between two requests). Check Zend_Session