Yes, spices can lose their potency when stored near the stove due to heat, humidity, and light exposure, which degrade their volatile oils.
Spices derive their flavor and aroma from volatile oils. These oils are sensitive to environmental factors such as heat, humidity, and light. Storing spices near the stove exposes them to all three of these elements. The heat from the stove can cause the oils to evaporate more quickly, diminishing the spice's flavor. Humidity, often present in kitchens due to cooking, can lead to clumping and mold growth, further degrading the spice. Light, especially sunlight, can also break down the chemical compounds responsible for the spice's flavor. Over time, these factors combine to significantly reduce the potency and freshness of your spices. Therefore, it's best to store spices in a cool, dark, and dry place away from the stove.
To test the freshness of your spices, rub a small amount between your fingers. If the aroma is weak or non-existent, it's likely time to replace them.