Welding Duty Cycle: A Comprehensive Guide

Although it might seem like turning off your welder might help it to cool down faster, the machine will stay hot longer if it is switched off amid its “cooling period”.
This is because a small fan, or several small fans, move cooling air through the vitally important areas of the machine when it is on.

I need to raise a point. Not all welders feature a fan, in this case, switching off when not in use will help, only if the over-temp has not triggered though. Plus, you can increase the duty cycle of any non-fan welder by blowing one into the vents. The increase won't be great, but could be worthwhile at lower settings.

https://weldingcentral.com/welding-duty-cycle/