6 to 8 was a 40 minute hold. 4 to 6 was about twice that long. In my unscientific tests, the 6 to 8 hold time increased element life by at least 20% versus firing all the way up to 8. There didn't seem to be any noticeable affect on relay life, but the relays on my big kiln last forever since they're housed in a freestanding box away from the kiln. They just don't get very hot compared to kiln mounted control boxes. That said, the relays on my small kiln last a really long time, too.