If you are making parts from 12L14, then it's probably safe to assume that your primary consideration is machining cost and/or cycle time, and not mechanical properties of the material. So the additional cost and time required for a stress relief operation before final machining would seem unacceptable for this particular application. Free machining alloys like 12L14 require less energy to machine, and as a result they naturally tend to accumulate less strain during machining operations.