Do you do a full Pre Trip everyday of driving?

Since I drive the same truck, and know it well, my routine is the same all the time:
Monday and Thursday I check all the fluids, unless I notice something on the ground.
Otherwise, every day, as I walk up to the truck I look for signs of leaks on the ground (I park in the same spot every night, so it'll be obvious) fire the truck up, listen for odd noises, listen for air to start building, turn on my ELD, start my paperwork while the ELD is powering up, then hit my ext. light test switch and do a walk around with sledge to thump my drives, put a gauge to my steers, check lights and check the exterior
Since I often pull 6 or 7 different trailers per day, my drives are thumped multiple times per day, unless you're deaf or blind, you can usually tell when something is off with a tire during the day, Monday and Thursday I put a gauge to my drives in the morning

If I notice odd smells, sounds, or a dash gauge is off, then I'll check it more thoroughly. When I fuel at night, I give it a once over. Boss/mechanic is usually poking his nose around all the trucks every afternoon

 

Obviously some moisture got in there, either from the loose bolts or the rubber cap not sealing well enough. That will be getting addressed at the next PM. IMO there's not enough contamination to merit an immediate service, but it won't wait long. Pull both hubs, inspect/replace bearings, new seals, new hub caps.

 

Personally, I'd be more worried about the contaminated oil than the small leak from the cap itself. You could of probably just snugged down the bolts, topped off the fluid and moved on but if the oil is so contaminated with water that it turned brown that requires a much more involved repair than tightening a couple bolts.