We get our information from Google, showing data from Google.com for US results and Google.co.uk for UK results. We do not collect data from Bing or Yahoo.
We update our data on SpyFu.com and SpyFu Recon Files once per month.
The most recent month is collected and given a name (everything that happened throughout March is called 03/01), and it rolls out to the site the following month. This usually happens in the first week. March results would appear toward the beginning of April.