Depends on what I'm doing and how the site is going.. When I've just started a site and it's slowly growing, tends to be multiple times a day, unnecessarily really but hey.
Once a site is established, couple times a week to look for new interesting trends and analyse date for link building, working on particular traffic sources, etc..
Wrote a bot yesterday that sends stats daily to my phone. It'll always be profitable, so daily is enough. Stops me obsessing over it. Bot uses http://www.airgramapp.com/
I have a script which grabs earnings from all my affiliate networks. That's pretty much just what I look at. I hardly ever look at Analytics data anymore. I check my rankings twice a day and then just worry about how much more money my sites are making.
Wrote a bot yesterday that sends stats daily to my phone. It'll always be profitable, so daily is enough. Stops me obsessing over it. Bot uses Airgram - Mobile push alerts for any service