Theoretically, would it be possible for a ship—say, a Harrower-class dreadnought, for example—to still be intact and in operating condition nearly 4000 years after its creation, during the original trilogy era? Or, alternatively, would it be possible/more viable to build a brand new one 4000 years later? (also, happy new year! :D)

Well, I suppose it depends on the conditions in which it’s being kept. Durasteel can be corroded, but I expect that if it was preserved well enough it wouldn’t break down too much. The Harrower-class is described as being very hardy. I’d be guessing, but I think that if you want the ship to last 4000 years you could probably get away with it. Obviously it would need refueling and recharging, but I wouldn’t reject it as a possibility. 

On the other hand, the ship’s weapons and shields seem pretty similar to those around the OT era, and it’s a pretty small capital ship, so it’s also perfectly possible to build a new one, assuming you had a blueprint. It would be expensive, for sure, and it would take longer than to build than it would to restore an old one, but I think either scenario would work well enough. If anyone knows of an instance where a ship lasted that long, please feel free to add on!

Hope that helps!

~ Jacen