[ariel]

There is an old saying that it is better to be young, healthy and rich than old, sick and dirt poor:-)

So it is with our sharpies: it is obviously better to get a sword with the original scabbard in a perfect shape than without a scabbard at all.
That being said, most of ( at least Oriental) swords dating 2-4 centuries had their scabbards changed not once and not twice.

Can’t remember the source, but Russian Cossacks had to get a new scabbard every 3 years. With all the Imperial Russian graft, theft and negligence this period might have been extended to 5 easily, to 10 likely and to 20 quite possibly. But they must have been changed at some stage of the game. Scabbards were deliberately exposed to all kinds of damage, - mechanical, climatic, just age related deterioration of organic components, etc,- to protect the blade.
Even assuming 20 years as a reasonable estimate, an 18 century Shamshir, kilij or tulwar by now is on its at least 5th scabbard of it’s working life only if it was out of military use around WWI.

In our ( collectors) case, storing swords within their scabbards invites rust.

It’s nice to have a scabbard, but it most likely will not be original and prudently stored separately.