The only thing about long duty hours which is a pain if not managed well is needing the toilet, especially if you have some type of condition in that respect. Pretty much everything else you can prepare for, as long as you able to - in some cases there might be some [silly] restrictions if in ceremonial dress, etc. I'm often surprised how many people do stuff like that and don't have simple things like a pack of travel tissues, a few sweets, etc. even if it isn't their first time. (Then there are things like toe exercises, etc. to help with circulation and so on).
As a minimum compact "kit" I have a Victorinox Classic SD, Olight i3E (i1R is a longer life alternative) and either some plasters or small roll of elastic medical tape, if possible wet wipes or sanitiser don't go amiss. Though less necessary with phones a pen and paper can also be handy to have.
If I can have my sling pack with me even better as I have a bottle of water, power banks, etc.
For the most part anything else quite frankly is a lack of fortitude, unless people genuinely do have things like a back condition, etc.
