You can buy the "pen sharpeners" from e-bay, tapered one end straight the other, I've had one for 20+ years, fantastic little tool.
There is no hard & fast rule for hooks/traces, change them when they need changing, might do 2-3 trips, might do 2-3 casts.
Also think before you dispose of them, I treat old traces like medical sharps, they get put in some sort of plastic tub/bottle with a lid,
when full I tape it closed & stick on a label that says "used fish hooks/sharps" because waste is still hand sorted in places.