protected function remember($key, callable $function)
    {
        $class = new ReflectionClass($this);
        $class = $class->getShortName();

        $lifetimes = config('forum.preferences.cache_lifetimes');
        $lifetime = isset($lifetimes[$class][$key]) ? $lifetimes[$class][$key] : $lifetimes['default'];

        return Cache::remember($class.$this->id.$key, $lifetime, $function);
    }