Before I really started to study the score, I've listened to this symphony like thousand times as a classical music lover (or nerd?), furthermore, this symphony was among my "most frequent played music" list back to my orchestra musician days. Therefore the "natural tempo" for me to hum this symphony is probably affected by those experiences, by recordings. I was very surprised when I found 54 is way faster than I used to; most recordings use the tempo around 38-42...