Updating a SERP in Keywords Explorer and Site Explorer can change the Traffic potential, Keyword difficulty (KD), presence of SERP features and positions of results in SERPs.

SERPs in both tools are automatically updated all the time, and it's dependent on the popularity of each keyword.

Keywords that are more popular would have a higher the search volume. The higher the search volume a keyword has, the more frequently we fetch new SERPs for it. This is anything from multiple times a day, to once in 1-2 months.

The Volume metric shows how many times per month, on average, people in a given country search for your target keyword. In Keywords explorer we use the 12-months average, and you'd have to hover over the graph to see the monthly average number:

Search volume and CPC are updated every few weeks, and at least once a month for each keyword.