I've never had this scheme involve any vouchers in the States; it's something that has to be keyed in by the hotel staff. The system worked like a charm all but once, posting anywhere from immediately to the day after check-out. The one time it didn't post, I asked on my next visit - they apologized and posted a set of points right away (after verifying I never got them, presumably). I've even received a double set a couple of times.