Manufacturers recommend checking and topping up AC refrigerant every year. Low refrigerant can ruin the system, so charging and cleaning belong in a workshop.
A car air conditioner works much like a refrigerator: it is a sealed system filled with refrigerant and dissolved oil. The refrigerant absorbs heat from the cabin as it evaporates and releases it outside as it condenses.
Manufacturers recommend an annual check and top-up; neglecting it can lead to failures that cost far more than regular charging. Because refrigerant escapes through micro-cracks and even through hose material, DIY sealing tricks do not help.
If the cabin no longer cools properly, drivers are advised to visit a workshop and have the system disinfected and recharged with professional equipment.