I am in my mid 30s, started my professional career in 2008. Hard to tell if when is a good time for doing it. My feeling is I should have done it earlier but I guess it depends on your situation. Maybe if you have an active social life and hobbies you love it will be easier at any point. If you have worked a lot and over long time I think friends/hobbies can fade, and it will be easier to fall into loneliness/depression if you quit working.

But, I think doing it early (say after ~3 years) has the advantage of settling/deepening the understanding of your work. Often the early years are super hectic and you try to be your best, neglecting things like mindful reflection. I believe sabbatical can help this, kind of like how sleep organizes and "cleans up" thoughts/memories. We need both the short sleep and "long" sleep.