The OLD HSK-1 requires about 80 hours of study to complete all lessons. If you can have an intensive and immersive learning plan, such as study for 4 to 6 hours per day, you will be able to finish HSK-1 in about 4 weeks. As for the NEW HSK-1, since the textbook has not been officially released and published, it would not be easy to estimate how long it would take to finish. It might be 4 weeks up to 8 weeks.