This was the best tour I did (our of four) in Rovaniemi. Braulio was accommodating and very knowledgeable. I knew it'd be nice, but (being a California girl) I didn't know how absolutely breathtaking this seemingly untouched trail would be.
First, I recommend using the Beyond Arctic's snow suits. We all invested in bringing our own snow parkas, pants, etc., but the snow suit is the way to go.
Despite being 5ish hours, it didn't seem that long. The terrain changed as we went higher up. Braulio had timed it so we had wonderful light during the whole trek. His pictures are stunning. I appreciated his photography since my hands were too cold to take off my gloves and fiddle with a camera.
I'd recommend doing a private tour, so you can go at your own pace. My 10 year old daughter joined us and had no trouble keeping up.