quality vs quantity
I will admit to a prejudice about amount of practice. I think that anyone serious about pursuing a martial art practices every day. However, the realities of 21st Century United States culture dictate that this "formal" practice time will be limited to the dojo's hours of operation.
Some will have the triple great fortune of a school with a high-caliber instructor, many class times and easy access. Others will have only one or maybe even none of those things. I believe that no matter where or with whom you train you should maximize your time on the mat. That means truly BE THERE during class, focus, give your best effort, etc. I know some people who have all three of the great fortunes and squander them by coming to class only to discuss their political and philosophical views. Their practice is hollow, their attention to the practice mediocre at best. Having the three fortunes does not mean you have the best practice, the best technique or the best views. It only means you're lucky. It's what you do with it that counts.