In the beginning it took me around a week. Then the workload became to much. Now it takes 10 days with 15 lessons a day (although higher levels have in average less lessons)
I would recommend you to start slow and steady. Don’t do your lessons all at once.
Use also other sources.
If you only WK for one year your kanji-powerness will leave your other abilities (acutal reading, speaking, listening) behind. Too behind. Unless you are intermediate level already. In that case the perspective changes.