register-preview-delay
register-preview-delay is a variable defined in `register.el
'.
Its value is 1Documentation: If non-nil, time to wait in seconds before popping up a preview window. If nil, do not show register previews, unless `help-char' (or a member of `help-event-list') is pressed. You can customize this variable. This variable was introduced, or its default value was changed, in version 24.4 of Emacs.