Please understand, I am aware that many of you here will disagree with me and that is fine. Just take a minute; this information might be worth considering.
About 9 months ago I read an article posted on a DVD tech specifications web site of some sort. They were writing about the lack of standards dealing with DVD life span and mentioned that there was a study currently underway to provide some sort of rating for different media to provide a life span index for consumers. They stated that this would probably take 2 years to establish. The comment I remember clearly from one of the lead technicians was that it was clearly established that DVD media burned at slower speeds had a longer lifespan. He didn't say how much longer but he was very clear.
This is not an argument like the -R / +R debate that rages without end.
To me, based on what I read, slower burns will last longer. I still burn at 8X rather than 4X when the media calls for it, but I don't want to risk lifespan just to save 2-3 minutes by pushing media past its rating.
Feel free to disagree. To me, the source was reliable. He had no bias, he was stating a fact.