Some say that there is a rhythm to our wandering mind that is to do with the actvity of the default mode network. This means that there is a rhythm to when our minds will pester us to do something other than meditate. I also heard that this means you can time your meditation to have maximum effect if you know about this rhythm. Does anyone know about this stuff ?

I am not a neuroscientist, but as far as I understand the whole default mode network thing is not even universally accepted by the scientific community. Personally, I just try to time my sits based on observing their quality after the fact, and noticing patterns.