You would be surprised how often your heat press goes out of calibration. Heat and pressure affect metal over time. The ability for coils to heat up, the resistance in the temperature gauge, and the constant pressure put on your platen can all cause heat presses to lose calibration.
How often should you check this out? The answer depends on your usage and the risk of producing poor-quality goods. A small shop can get away with checking their heat press once every quarter.
Typically, a small business owner keeps a close watch over their business and equipment, and they notice when things aren’t running correctly. Quarterly checks, and having the awareness that your press can fall out of calibration, are often good enough. But, if your business is a larger shop where the heat press pushes through hundreds of garments/goods every day, you should probably run weekly checks on all of your equipment. A heat press off its temperature for a few days could mean a massive span of poorly decorated goods.