code: @Destroy(priority = AutumnActionPriority.MIN_PRIORITY)
      public void savePreferences() {
          final ObjectSet<Preferences> preferencesToFlush = GdxSets.newSet();
          for (final Entry<String, Preference<?>> preference : preferences) {
              final Preferences preferencesFile = namesToFiles.get(preference.key);
              preferencesToFlush.add(preferencesFile);
              preference.value.save(preference.key, preferencesFile);
          }
          for (final Preferences preferencesFile : preferencesToFlush) {
              preferencesFile.flush();
          }
      }
docs: Saves all current preferences. This is a reasonably heavy operation, as it flushes all preferences files - by
  default, this is done once, before the application is closed.