It is hard to tell you exactly how long RtK will take, as it is a function of how much work you are willing to put in on a daily basis. The fastest I have heard of is about two weeks to complete the book (reviewing would still have to continue), whereas others has taken it slowly over many months. I'd say the most important thing is to find a pace that you can keep somewhat consistently.

screamingfields wrote:

Also is Heisig's way good enough for learning Kanji? Or what is the best way to learn vocabulary?

RtK is a good way to learn the kanjis. People seems to prefer learning their vocabulary in many different ways, so I'd suggest you try looking different methods up and just test them for yourself to see what works for you.

2042/20 = 102
2042/30 = 68
2042/50 = 40

I'd recommend doing 20 or 30 new cards per day. The reviews really start to stack up.

As for if RTK is a good way for learning kanji, I would say yes. However, this really depends on you and you may love RTK or hate it. If you do complete RTK you will handle vocab with ease.

Until you know how many reviews you can handle daily, it's better to stay on the safe side.

But that way you'll never find out how many you can handle, unless you're limited by time and the speed of your reviews.