Knock Sensors

[X53Jay4.8is]

For those of you that have V8 equipped X5 E53s have you ever had a knick sensor fail? If so what were the miles on your unit. I ask because I am getting ready to re-seal the timing covers on my vehicle, do the vanos, timing chain and guide rails. I am of the type that if I am in there I may as well change whats old in the name of preventive maintenance but the knock sensors are pretty costly and rarely do I hear of them failing on the E53s V8s. So what are the thoughts on this.