I guess it depends on you. For me to be able to do it with English, it took me years. Still now sometimes with a monolingual dictionary I feel not certain and use the English-Italian dictionary.
I noticed though that Japanese in a certaing way is easier. I can already read a Japanese book faster than I could read an English book after the same amount of time of study (lol still 1/2 hours per page
). Kanji help much more than reading all words written in our alphabet. A kanji which suggests the meaning of the word helps much more than hoping to find a word in English which sound like a word in my language.