Apparently John Sherman recently had a part of his rappel anchor fail where he had girth-hitched a Mammut Dyneema sling to another sling. There is a long thread on this at Supertopo
There was also some related testing of these super-thin slings that showed that they lose 1/3 of their strength after 2-3 years. They are only meant to be used for a short time. I didn't realize that Mammut was stating that.
Another reminder to make sure to eliminate any nylon-on-nylon in any anchor.
"But what is happiness except the simple harmony between a man and the life he leads?" – Lord Byron
So instead of girth hitching two slings around a tree to rap from, I used a biner. As soon as I got 20 feet down the rap,my partner yells "wait the gate is open!" Luckily I could climb up without letting go the brake. I went back to girth hitching.
"Everyone should have a plan for the zombie apocolipse" Courtney