code: def should_regenerate(self, response):
          
  
          if response.has_header('Last-Modified'):
              last_modified = parse_http_date(response['Last-Modified'])
              next_regen = last_modified + settings.BETTERCACHE_LOCAL_POSTCHECK
              return time.time() > next_regen
docs: Check if this page was originally generated less than LOCAL_POSTCHECK seconds ago