I used to think like that a lot but more and more I wonder if it is really a good idea to go through life in a way so you have it nice when you retire.
Literally, I am billing < 20 hours a week, and unless I become disabled and/or get dementia/Alzheimers, I feel that I will like doing what I am doing in some form or other forever.
I've done a lot of different things in my life, and this _is_ having it nice. It's far nicer than the "retirements" of many of my friends in their 70s, though I will grant it is not as plush or completely free of pressure as my parents' retirements as school teachers/administrators.
I'm also travelling in SE Asia so my outgoings are very low. I didn't realise how cheap it was here. I'm bringing in nearly 5x (before tax) of what I'm spending.