Confusion about accuracy vs tolerance of an operating resistor
Like awjlogan said, the nominal value for that part is fixed after you measured it.

Over time you will get drifts based on that nominal value. Humidity, power, temperature, time, overload and other things will affect the value in the later life of the resistor.

As an example, here is a table out of a Vishay datasheet:


As you can see there are several mechanisms which can have a serious impact on the value. The typical value shows, that the most critical things for these resistors are moisture and time (max. 3% and 1% after 10000h).

Depending on the make of the resistor different mechanisms will have different effects, so check the datasheet of the resistor you are using.