Is there a recommended warm-up time for the 402x Series precision sensors?

There is no required warm-up time for the 402x Series precision sensors. These units draw very little current so there is little to no self-heating to account for. The sensors can be used immediately without delay and still achieve their accuracy specifications. 

That stated, if you deploy the sensor next to other equipment that does undergo self-heating and requires time to stabilize, then it is in your best interest to apply the warm-up time recommended by for that other equipment. Remember, too, that the sensor must still be operated within the temperature range specified in its datasheet in order to ensure rated performance.