I think that the distance is slightly long, but you may be able to build up to it. I do 6 miles on the way in (train assisted) and then do 15 miles on the way home (not train assisted). Generally that is fine. It is a pain when I have a cold etc (mainly winter). It was also not great in the snow and ice this year and I also used the train both ways then. I guess if you have a car then you have an alternative, we went to one car and I don't have it as an option for a couple of days a week.