While surfing UK Climbing, found this article about fixed anchors. The Brits at the BMC have done studies on pin anchors. They are starting to frown on old pin anchors as they are finding them too unpredictable. In this article they are in part responding to requests by groups and individuals for free new pegs to be donated by the BMC. The BMC is apparently going to respond with. "We won't supply free pegs as they make unpredictable long term anchors".