The OP title is fallacious. Login counts as an intensive database query (rightly so). The forum software limits repeat intensive database queries (which include searches) by enforcing a reasonable interval between queries. This results in a better user experience for every single user of the site. Ultimately, this means the enforced interval must expire between logging in and initiating a search (which is only what, 20 seconds?). If that is too big of an issue for you consider quitting the internet.