Early postdoc is probably the sweet spot for (individually) working on what you love. As you become more senior, responsibilities start to accrete around you.

Early postdoc is probably the sweet spot for (individually) working on what you love. As you become more senior, responsibilities start to accrete around you. You can make more progress on something, but you start to do so by supervising others and writing grants to make it happen, rather than just doing the work yourself. This can be satisfying, but can also devolve into endless paperwork.