Let's be honest, if you have an S Class, you would likely travel by plane/first class, not sit 10 hours in an S Class, as comfortable as it is, it's a matter of time lost.
Actually, a lot of people buy an S Class (or the equivalent Audi, a well-kitted A8L) and then put many, many miles on them. It's not a coincidence that there's a bunch of 80's S-Classes with over 300k on them, and 90's S-Classes and A8s with over 200k. These are being driven by businessmen who will be able to write off much of the significant recurring expense of putting many miles on a german car.
In short, these cars are not made worth a fuck. They use components guaranteed to degrade when components which would hold up just fine are available. Rubber bushings (not sure of the material) and EPDM vac hoses when they could be made of polyurethane and silicone respectively and last the life of the vehicle. And everything is crammed into as small a space as possible, because that's how it is today. I have big fat meaty hands, a lot of these cars require me to take some stuff off so that I can take some other stuff off before I can get at a third thing. Even if you have a lift you're best off removing the engine in many cases because you still can't get access otherwise. But sadly, they don't have an engine harness, so you have to disconnect forty things to pull the motor. Perhaps literally; just the coil packs and injectors account for sixteen connectors on a V8.
S-Class and similar are for people with lots of money, and/or people who are playing games with taxes. Not for the plebes. You can own one only if you are a mechanic. The saying is that there's nothing more expensive than a cheap Mercedes. The same applies to VAG cars. You can't afford to own an old Audi if you don't turn your own wrenches.