In my opinion yes, but my desire to have a back-up should I run late on a day's ride and end up in darkness has come from experience. And having a dynohub means I don't have to ever worry about batteries for a front light (ergo, read my opening sentence in which the batteries died).

Compared with the weight carried by most touring cyclists, the losses in the dynohub are minimal, in my experience. In addition, I have used my touring bikes for other purposes such as commuting, and of course a dynohub light system certainly works well for me in that case.

I have two Shimano dynohubs standing by now to be built into the wheels on our current touring bikes.