Accounting for temperature changes in circuit design
The forward voltage of the LEDs will drop significantly with a temperature increase of 125°C, perhaps 0.7~0.8 volt for a string of 3 (check the datasheet for the particular part). That will mean that the current will increase by maybe 25% at high temperature. Since the allowable current probably drops to zero at 150°C Ta this is the opposite of what is desirable (will tend to kill the LED even more readily at high temperatures). On the other hand, 25% will not be all that visible a change in light output. 

Bottom line is that temperature is not too important to visible light output if you have at least 1 volt per series LED across the resistor and temperature change isn't insane. Light output also changes with die temperature, so the current isn't the only factor. 

You can typically ignore the resistor change in temperature - even a crummy resistor will not change more than 100ppm/K which is 1% for 100°C change.