How often does data get updated or refreshed?

This depends - but endpoints are all cached to around 1 to 5 minutes and you can expect most data to be updated at similar intervals unless otherwise specified. Pro API (paid plans) generally have faster update frequency, i.e. 30 sec for simple/price endpoint.

This also means that as a user, you should try to throttle your response to ensure that you are not wasting bandwidth by making calls too frequently.