I've studied Japanese for 5 years, and have a vocabulary around 20,000 not including numbers, and I am still able to learn words on a normal basis. I've seen a complete dictionary in Japanese, and since it contains all dialects from all time periods, I was only able to read from 10-15% of the words. I'm sure the entire Japanese vocabulary is from 200,000-300,000 words, maybe more.
On an every day basis such as communicating normally, less than 5,000 words are uses , and I'm estimating around 40,000 words would be required to get through with hardly ever hearing a word you don't know.
Do you study Japanese?