It's unrealistic to expect someone to spend 30 full time days (6 unpaid weeks) on that kind of material in one go. I've done it myself and gave up multiple times in the process. More than 2-3 days full-time and I burn out immediately. Even doing it just on nights and weekends is incredibly tiring (especially after a normal days work). It's incredibly tiring to do leetcode or similar for 8+ hours/day every day. Especially in the beginning when you start out - because you will feel completely hopeless with the process.
Just FYI - this interview process isn't a one and done thing. You have to refresh yourself at least every year with ~80 hours of prep. Otherwise, you're going to be really bad at it when you search again.
Definitely not one and done! But I doubt you will be searching every year? Maybe once every 5 years hopefully on average. And in the sister comment I mentioned taking unpaid leave to do it, which will be paid by the next company paying you more salary. If I lived in the US where this would make a difference I'd be doing it now. However where I live there is only Google (not FAAN etc.) and they don't pay as much as in the US, so probably not worth it.
Just FYI - this interview process isn't a one and done thing. You have to refresh yourself at least every year with ~80 hours of prep. Otherwise, you're going to be really bad at it when you search again.