For me, it isn't about length, but rear overhang. Most intercity buses have the tag assembly very close to the back of the coach. This makes for very high road stability. You can actually feel it at speed.
The reason mfgrs move the axels forward is to take the weight off the front axle which is usually maxed out at 15-17klbs. This contributes to "tail wag" and swingout which is minimal in a long wheelbase coach.
I shopped an older 317" wheelbase monaco, which is probably the longest out there in a 45. Rides like on rails. The disadvantage is it doesn't bend in the middle.