I agree that this may vary from media to media, and that some medias burn better at their rated speed or even at higher speed, but in my experience these are oddities, and most of the medias I personnaly used liked lower speeds.
Most people don't take the time to check each media batch for PIE/PO/PIF errors to see if the media burns OK at higher speeds!
Furthermore, if PIE/PO/PIF errors scans right after the burn are considered as an indication of the media durability (less errors = more lifespan), this is far from being an exact science. I'm not 100% sold to the theory.
So my opinion is that Chas' advice is a good rule of thumb. :iagree: