The caution that more than 3 1/2 hours of a training run brings more risks than benefits seems to be a common one. It is not just her opinion. That said, people who run ultras run much more but most don't get into that space unless they have demonstrated to themselves that they are durable.
20 miles is likely the American standard "long run" because it is a nice round number. Countries using the metric sytem (other than Canada which shares lots of things including running programs with the US) generally treat 30 kilometres as a long run. That's 1.4 miles short of 20, yet European runners do not seem to fair any worse than Americans.
You will want to remember that you're going to be on your feet a long time. It will feel different once you get into the 20+ range, but at that stage you will have an hour or so to go, so just keep on going. If you need to walk for a while, walk, but do so quickly so you don't lose that much time.
Besides, once you're in the taper period, it is too late to change your training. Unless you plan to skip the target run and do something later, this is your opportunity to see how the program works for you. Once it's done, you can stop to consider whether you would like to see whether the next time round, you might want to stretch the 3 1/2 hours to 4. With a full marathon under your belt, 4 hours for a training run won't sound so bad.
Post a reply on the Bulletin Board