Yes. You can go part-time now. With the caveat that you may at some point in the future have to go full-time again for a while.
If the math works out that you've already got the 'stash you need, as long as you don't touch it before you're 60, why not go part-time? Frankly, why not go part-time anyway, if that's really what you want to do? You're already in a really solid position.
Your future life is full of unexplored possibilities. Don't assume you have to follow a specific track to find the optimal one. Choose the one that's optimal right now. You never know what opportunities will arise for you later on.