My experience is similar. Started learning English and spent eight to nine hour per day, but it was completely my own desire. I fell in love with it after many years of hating it at school. Is it the only way? Nah, for sure. Does volume matter? Hell yes, but Not many people can / have the opportunity to keep up with such volume. So, I tend to advise prioritising consistency over quantity as it yields better results in the long run.