Many times a day unless I’m really busy with something else. But, our site is still relatively new and we are waiting out the seemingly never-ending sandbox.
Still, it’s good to keep track of where the traffic is coming from to have a pulse on what is working and what is not. Especially if you are running a PPC campaign. Most of those are fraudulent traffic, and the only way you would know is by checking the stats detail.
For the record, we are using StatCounter and AWStats.