Ah this is tough! When I switched careers I commuted into DC (mostly by train, but driving to our local train station) 4 hours a day total for one year. It was nearly exactly one year because when I got a scheduled promotion at the end of that year, I immediately moved into an apartment I could barely afford in order to avoid the commute. Lots of people in my hometown commute, but it took up all my time. I’d work, commute, and sleep, having to save everything else for the weekend. I eventually learned to sleep the entire train trip in the morning and often some in the evening, but I never felt the train was relaxing or “me time” the way some people report.
If you only have to trek in 3 days a week, that might be more sustainable, and the boost to your career is good, but I think it’s really up to how well you know yourself and your ability to cope with that situation. Good luck!