How often companies should send out customer service surveys?

Customer surveys should be done everytime a purchase was done or at the time of inquiry. This shouldn't be costly as the company can always include as survey form along with the product or thru e-mail. This is to gather information direct from the customers. Consolidation will be the discretion of the company's officials. 

Thanking you , I regret unable to paticipate and answer due to lack of infornmation as well as experience in this side .

Regards

These surveys, sometimes referred to as “relationship surveys,” are best used with customers that maintain consistent interactions with your company, such as a retainer arrangement or SaaS model. In terms of frequency, we generally recommend semi-annual surveys for our clients.When customers recognize your company’s commitment to listening and acting on their feedback, most will happily set aside a few minutes every six months to provide input. In rare cases, once a year may be appropriate – but only for companies with modest changes to the business or competitive landscape.