I've only done a 24 hour, but here are some tips. Take extra sets of clothes - is this a relay or is he doing it solo? ANyway, when he comes in, he will want to change sets of clothes, shorts and shirts; and of course, he will need lots of layers. Take good amount of socks. I used to package up my outfits in separate plastic bags so I didn't have to think too much, but just grab the next outfit and go. If he is solo, he may need another set of lights in the charging area or even if he is doing two night relay sets, he will need extra lights in the charging area. Take foods that you can eat easily and will not bother him, i.e. already baked potatoes, hot drinks, chicken, sweet potato, etc. and, of course, all the bars and things that he normally eats. All your tools for bike maintenance; extra tubes, etc. Lots of water and if it might be muddy, extra water and stuff to clean bikes, rags, buckets, etc.