This is related to bug 698275, which did not cover all cases.
The problem here is that the dconf can in certain situation claim
that everything changed (path "/" changed), which GSettingsBinding
propagates to a GObject property unconditionally and GObject's
property setter (g_object_set_property()) also notifies about
the property change unconditionally, despite the real descendant
property setter properly checks for the value change. After all
these false notifications a callback on "notify" signal is called
and possibly an expensive operation is run.

Checking whether the value really changed helps in performance, for
which were added new e-util functions:
   e_signal_connect_notify()
   e_signal_connect_notify_after()
   e_signal_connect_notify_swapped()
   e_signal_connect_notify_object()
which have the same prototype as their GLib counterparts, but they allow
only "notify::..." signals and they test whether the value really changed
before they call the registered callback.