Gichin Funakoshi practiced karate everyday, granted that he was a pro.
At one point he became a "pro" (that is, full-time dedicated to karate); however, before that he was a schoolteacher. During that time, if I recall correctly from "Karate-do: My Way of Life", he still trained daily. The book is a worthwhile read for anyone who wants to explore the issues of "way of life" and "how much is enough", because what comes forward quite clearly are one person's answers, understood as such. Funakoshi's daily training wasn't the result of a formula of how many days a week to train; it was something he did because it made sense. Indeed (and I may be misremembering, it's years since I read the book), but it seemed that the daily training wasn't the result of a one-year plan or five-year plan or life plan, or any plan but the plan of the moment. At the end of his day of teaching, he would start walking to the dojo, because then -- right in that moment -- it made sense to do so. That seems to me like a good barometer of "how much is enough".