Because it will be. Projects can be disassembled with the help of a large hairdryer or a heat gun. Heat resistant gloves are a must. Temperature is always a concern when using hotglue in displays. Plugging the glue gun into a temperature controller is the key to efficient use.
All guns get hotter when left plugged in, even to the point of discoloring the glue.
Hotter glue is runnier, more dangerous, and may melt synthetic materials. There are various options. Autotransformers, still used as motor controllers for shop equipment, allow very precise control of the voltage, and therefore the temperature of the heater element. There are smaller electronic controllers used for soldering irons or woodburning tools which work quite well, though their calibration varies. Household ceiling fan controllers can be wired into an outlet box, perhaps on the end of a grounded extension cord.