Is it recommended to leave the UVC light running at night? If this is not a good option, how long does it take to kill germs?

This depends on what power of light you are talking about. But such 180-watt tube lamps are far too powerful!

The equipments would begin to tarnish.

The lengths of time necessary to kill various bacteria, fungi, spores and viruses are different. Usually, 15 minutes is more than enough to kill/inactivate all forms of micro-life with a 95 watt light in a 40 m2 room.

While some bacteria, spores and fungi take longer to inactivate, for most coronaviruses, 10 minutes of UVC exposure is sufficient in a 40 m2 room.