Exactly what I needed to prepare well for the 45 k...

Exactly what I needed to prepare well for the 45 km Swimrun in May. I have never run longer than 23 km, and this will be 38 km running with 1500 meters. That is why I needed information.
Years ago I did the same test as preparation for the Marmotte. It gave me so much peace and confidence to know what to watch out for during your training, that I got on the bike with more pleasure. Now that is the same again. Thanks.