I had a job where I could do this. On any given week I worked normal(ish) hours, but I had pretty close to full control over when and where I worked, with significant autonomy on what and how. I spent most of my afternoons outside unless I really felt like working on my project. At the same time, being at a company gave me resources, teammates and scope I would have struggled to recreate working on my own open-source projects. I had just come off a one-year break and I ended up enjoying working more than I did not working. It's a real shame that we can't have more jobs like this; it requires giving people a level of trust and autonomy most organizations can't stomach.
If I could arrange a role like that into the indefinite future, I'd have absolutely no questions about working well into my 60s, and not at all thanks to a "lack of creativity".
Even so, the freedom to... saw/split/stack firewood when the weather was perfect, build a movie nook for my wife, go on bike rides on a Tuesday afternoon in a warm breeze, take our dog on a long, leisurely walk at a local park, read a book in the shade out on the deck...
...or pre/post-pandemic visit a brewery or winery on a slow Thursday (and all other forms of travel that are less ideal right now.)
But also FIRE doesn't demand that you "work extra hard" during the accumulation phase. At least, I have been fortunate enough to avoid that fate. I've rarely worked overtime in my entire life as a software developer. And of course, given this career and income, living within my means (actually well below them) doesn't mean horrible deprivation, either. Sure, I can't go on a $20k weekend trip on a whim (at least not regularly!), and we have to research our options for vacation so we don't blow a lot of money, but again - it doesn't take much creativity to have a really rewarding life that doesn't necessitate spending at or above your means. (Again some of this assumes you have a "good" income. There are stories of those with lower income making it work, but the challenges change!)