George S. Ledyard
Just an aside...
Current understanding of how the brain "learns" is that it is far more effective to do something for a relatively short period every day than it is to do it for a longer period all at once. So, it would be better for your actually progress to train one hour each day than to do the same number of hours compressed into two days.
Since it seems that getting to the dojo is the big hurdle for most folks, rather than how long they are there once they get there, one can see why folks would find that the twice a week option is the easiest to do. But if they made three or more trips to the dojo, even if they didn't train as long on the nights they went, they would progress faster going more frequently but training a bit left each time.
I think twice a week is fine if one has something to work on at home a little each day. Hitori waza, breathing exercises, weapons forms, all things that one could take 30-40 min to work on a day. I have a mat to roll out at home to work on. When time/distance is an issue, you find what you must.