Why does my blade get hot so fast?

Blades getting hot is not avoidable.  This is normal for any metal on metal contact, which heats metal over time, especially for the newer model, modern clippers which have much higher speeds. 

The higher the speed of your clippers - or always running multi-speed clippers on high - the faster a blade will heat up. Use a coolant spray or dip to quickly cool the blade when hot to the touch, and always oil before and after using a blade. Oil lubricates the metal, reducing friction, which reduces heat  If you don't have coolant, you can swap the hot blade for a cool blade the same length, or stop and give the hot blade time to cool.  

If shopping for new clippers, it's useful to choose a clipper with a slower low speed to avoid fast blade heat-up. Look for a 5 speed clipper, or compare low speeds when choosing a new clipper. Older model clippers were about 2,000 SPM on high.  New models are closer to 4,000 SPM. Double the speed means blades heat up twice as fast as they used to. 

WARNING: Keep in mind some coolant sprays do lightly lubricate, but will never replace the need to lubricate your blade with oil.  Coolant sprays can dry parts over time and residue can build up with frequent use. The cleaner in most coolant sprays also removes oil.  This slows down a blade and can make even a new blade seem to cut like it's blunt, due to increased friction, the blade not being able to move and cut freely, or product residue build-up.  Always thoroughly clean your blade after every use, then re-oil blades after cleaning, oil before storage and oil before every use

TIP: Sometimes what you think is a blunt blade - is actually just a dry or dirty blade that needs a good clean and oil!