The Turbo fans will fog when hiking, but it will also take them a lot longer to do so than a regular goggle. For instance, I spent last weekend at Berthoud Pass. It was snowing the whole time so I was wearing my Turbo Fans. I just leave the fan on High (against instructions) and hiked away. We were doing 600-800 vertical hikes and only towards the end of the last hike did I get some fogging. It was out of the way of my vision and quickly went away when I stopped hiking.
For a really high moisture content spring day, you'll see more fogging when hiking than say mid winter. More often than not, I am fine and do not have to change out my goggles. I still keep the other pair of Turbo fans in my pack and on occasion I have had to swap. It's rare though.
So if you are spinning lifts, I doubt you'll have a problem with fog with Turbo Fans. Same thing for short hikes. All day tours, I'd keep a back up with you, just in case.