allout-widgets-time-decoration-activity is a variable defined in `allout-widgets.el'.
Its value is

Retain timing info of the last cooperative redecoration.

The details are retained as the value of

Generally, allout widgets code developers are the only ones who'll want to
set this.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.