@Aaksz  Hello, 

Range extender generates heat when in use as other electronics, as different electronics varies in CPU, power, thermal design etc., they could feel different on the appearance temperature.  If you use RE within the range of its Operating Temperature : 0°C~40°C (32°F~104°F), this operating environment has been tested to be safe in the in lab and should not have any safety hazards.  You also got a chance to compare the replacement RE200 and found both RE act in the same way, this should be the common temperature on this equipment, and you could take it easy. 

Here are also some tips that may also help : 

• Put RE in a cool and well-ventilated environment
• Put RE in an open area and avoid enclosed space like cabinet. 
• Try a different wall socket 
•  Keep RE away from direct heat (like fireplaces and space heaters) or excessive sunlight.

If this is still a concern for you, may I know the temperature on the RE, the working temperature and its location (kitchen, bedroom etc.), thank you.