I understand that if I have a permanent ID card, and I leave HK without returning within 3 years, I am downgraded from ROA to RTL. What's the difference, exactly? It looks like there isn't any difference, on the HK Gov website, but there must be. Also, is there a time limit on RTL? What if I stay away ten years or more? Lastly, do the cards need to be replaced after some period? I'm weighing up whether or not to go permanent. Thanks!