How can I change the frequency of pulse surveys?

Winningtemp's standard is once a week to be able to measure temperature "in real-time", but it's up to your organisation to decide how often you get surveys from Winningtemp. 

You get one and a half week to answer a survey until it's inactivated if you get surveys every week.

As a system administrator, you can tweak the survey interval if you go to Admin view - Surveys > Standard survey > General settings.