As a general rule, I never burn at the top speed for a disc. I found, if I burnt at 8x, I got a coaster - at 4x every disc was perfect. Have bought several packs & found them well worth the money.
I'm using the disks for backups on a PC. I guess if you were using a DVD Recorder from a TV, you might not be able to control the burn speed and could run into problems.