Haven't know any better the last decade. Tying a backup prusik on you leg look is uncomfortable and if not positioned right will open up the leg loop buckle.
As for old carabiners; I just replace them over time. Aluminum doesn't have a minimum threshold for fatigue (not sure if that is the correct English term). I'm slowly upgrading to lighter, stronger and snag free type of gates (keylock for screws or those fancy things for the clippers).