You can clean your bidet seat as often as you clean your toilets, which is to say that once or twice a month should suffice. While cleaning, take extra care to ensure that the nozzle remains clean.
If your bidet seat has the functionality, you can have the nozzle come forward while cleaning. And use a mixture of water and vinegar, along with a toothbrush to clean the nozzle properly. Doing so will kill all the harmful bacteria that may have found a home on the nozzle.