A long running Puck that shows sensor values in the name, why could it stop after a day?

Are you using up to date firmware (1v93)? You could check process.memory().used and see if it's changing at all (which would indicate a memory leak).

Also, you could try removing the console.log (or just setting console.log=function(){};) - I did fix some problems recently (which haven't made it into a release) which meant that if you printed a lot of data in one go while not connected it could cause some problems.