I use the Hitec coreless digitals on flight controls with no problems. These are the 5925/5945 series, the step up from the digital non coreless 5625/5645's. As with all my Hitecs, I use the servo programmer to burn them in for a half hour or so after I program them.
I have not had one failure. Some guys may tell you differently, but I feel the Hitec coreless digitals are some of the best servos on the market. I like the fact I can program endpoints, speed, deadband, and such. Makes it easy to set up a control surface. I fly DF for now, but would not hesitate to put them on turbine powered models. I know many folks up here that do just that.

Brg,
Jeff