Clay compiles data from a number of different sources, and refreshes profile data millions of times a day. The refresh rate depends on a number of factors, including how frequently those contacts are visited, how often they have changed their data historically, and other signals.
On average, that means Clay refreshes data for a profile every few months. That said, the refresh rate could be as frequently as every week, or as infrequently as every year. We're working on a few improvements to make it more clear when data has refreshed, and make it easier for you to refresh data yourself — stay tuned.