Technically, 1.

If you read the help file, it says something to the effect of:

Because we support multiple searches, and because we don't want people constantly flooding GNet with search requests, we are going to limit you. You can only start a *new* search every 5 seconds. If you try to start one before that 5 secs is up, you'll get the message window telling you to hold your horses for a couple more seconds.

Clear as mud hopefully - Snakeman out.