Re: How much training per week?
In my experience, most adults need a minimum of three times per week to make staedy progress. All of the Godan and Rokudan level teacehrs I know spent a substantial period, ay some point in their development, in which they trained six or seven days a week.
It all depends on how good you want to be. I tell the young students to train their brains out while they still have the opportunity as it only gets harder to keep the commitment as they get older with the demands of jobs and family.