Due to the instability of npcd (as soon as memory or cpu resources get tight npcd will just error out and exit) it is necessary to keep a close eye on it in case it decides to stop playing nicely and you start losing stats.
I use a simple little bash script that checks if npcd is still running or not and just restarts it if missing. Works like a charm and I don't have to wait for icinga/nagios to make the check and then sometime restart the service per action handler.
#!/bin/bash while true do sleep 5 if [ ! "$(pidof npcd)" ] then service npcd restart fi done