It mostly depends on the driver. The road is not moving, just your vehicle. Drive at a speed appropriate to road conditions and all should be fine with new or used. Slow down and then slow down some more, remembering you are on vacation. Many of the horror stories you will hear are just exagerations from some that like to make themselves seem more adventuresome. Just telling someone you drove all the way to Alaska and didn't break anything, isn't much of a story..
The bigger rigs seem to have more issues, especially some of the large diesel pushers, that isolate the driver from much of the road sounds. Now the very experienced DP drivers don't have many problems with road damage, because they have developed a good feel for their RV and know when they need to back off and slow down.
Over the years I have done just as much damage to my rigs driving in the lower 48 as I have on the Alaska Highway. Colorado roads have caused me more cracked glass than Alaska. Last trip, 2011, some unseen road debris kicked up and bent one of my truck camper tie downs, in southern Alberta, on a nice highway. Stopped at a shop in Montana and bought a new tie down.
As mentioned above, just plan on normal maintenance as it is a long trip for most of us. I plan on about 3 oil and filter changes with a lube, plan on wearing about 1/3 or 1/4 of the tread off a new set of tires, may change the air filter once, because of bugs, tree fuzz, etc. I put 1/4 inch hardware cloth behind the grill to help keep the radiator clean, sometime a screen on the outside of the grill if I can get by without over heating the engine. Doing this currently on my Chevy truck instead of the hardware cloth.
A mid sized Class C is a nice rig to take on the trip. Over the years we have made 5 or 6 round trips with a 24/25 ft C. The last four round trips have been in a truck camper. We just take whatever we own and with just my wife and me, it works fine. However we are considering taking our 5 the wheel next time, whenever that might be.
