Most of the stuff I store in DTP is stored in the one database. I have other databases for such things as email archiving, but they are only really used as archives. I do not use them from day to day.
When I perform a search in the search window I have to remember to specify the database I want to search. I often forget to do so (even after 7 years of use), enter my search term, then have to wait for the search to go through EVERY database while watching grass grow.
It surely must be possible to set up some search defaults, including the default database to search. It would save a lot of frustration.