It depends who you ask. To be 100% sure you need to clean (PBW) and sanitize (StarSan) every bottle, every time. I did that when I started brewing, but don't any more and I've never had off flavors or contamination due to it. We had to replace our dishwasher in the last year, so now I clean them well with water right after using them as you do and pop them in the dishwasher on the sanitize setting a few hours before bottling and cut out the StarSan step. I do double check the bottles before I load it though; I don't trust it to clean bottles.