Just stay the right amount ahead.
I like to stay ahead in preparing for things. But if you get too far ahead in your preparations, there are several hazards that can pop up.
First, your advanced preparations can be unusable, because situations evolve over time. If I’m prepared twelve weeks out, but something significant shifts at six weeks, then my advanced prep becomes a liability because (a) I’m tied to that work and (b) I may have to do work twice instead of once. Related, ideas need time to percolate. If you do the work before you’ve allowed your thinking around a project to settle, you end up with a half-baked solution that will need later revision.
Second, advanced preparations can leave you with free time later. Why is that a problem? In my case, because free time comes with creative ideas. Creative ideas lead to projects and more demands on your time. Most of the side projects I work on evolved out of being so on top of things that I had unexpected free time.
Work ahead! But not too far ahead.