I am not yet an expect in the field of ultra running but one thing I have learned is the importance of being confident and comfortable with the gear you are using. That means
you have to try out and test every item that you'll need on the day/night.
Shoes, socks, headtorch, jacket( 100% waterproof ) gels ...
Having said that
I have just got in from running from Wallingford back to Oxford , most of it in the dark. My torch was OK but my nephews was crap. I had a skinz suit on
with a couple of thin layers over it and never needed to put on my Jacket.( I would have if i'd stayed out longer )
Between Abingdon and Radley it was a bit sticky under foot but compared to last year it was 100 times better.
I feel confident i'll have no problems from 30 miles out. All I need to do is conquer the first 70.
I've got a big grin on my face thinking about it.