Temperature regulation is really important as the length increases. I am not good at it to be honest having made some really big mistakes in 24h and longer races. I thought I had posted a quote related to Scott Dickson but must have forgot to. The gist was he needed another warm woolen jersey on the second night of PBP. IIRC, he finished with the lead group in 1979, 1983, 1987, 1991, 1995, and 1995. He won it a couple years. (Yes, I know the premieres and results are no longer thought in those terms, it was back then)
Jumping into a 24H race or test without some experience riding in the middle of the night is a little risky. The only think I remember from Loudeac to Fougeres in 2015 was two French riders with dead batteries sucking my wheel and shivering my derriere off. So, might be a good idea to try a midnight to 6 am training ride first.