 How long and how often should I look at my 401k? How often should I mess with my 401k? So let's tackle that right now. We've been told that if you do it too much, it can lead to bad investment decisions. And just got this from BlackRock. They said that shifting stock investments once or twice a year towards the better performing sectors can result in some pretty big gains. It makes sense to me. I'm sure you guys have seen this many, many times. It's like porridge.