[Raynor]

Originally Posted by The Sixth Wizard

Are orcs immortal?

I personally doubt that, unless we are talking about the maiar orcs mentioned in the Myths Transformed. And if the orcs in question have mannish blood, they aren't immortal:

Originally Posted by The conclusion of the Quenta Silmarillion, Valinor and Middle Earth before LotR, HoME V

Now all those who have the blood of mortal Men, in whatever part, great or small, are mortal, unless other doom be granted to them

Originally Posted by E & E

You'll remember that the goblins in The Hobbit recognized Glamdring and Orcrist, two elvish swords that likely had not been seen for thousands of years (and even if they had, they hadn't been wielded by elves since Gondolin's fall).

It is also presumed in the Hobbit that the trolls aquired the swords through looting:

Originally Posted by A short rest, The Hobbit

- I could not say, said Elrond, but one may guess that your trolls had plundered other plunderers, or come on the remnants of old robberies in some hold in the mountains of the North.

If the orcs in question were some previous owners of the swords, (and, even more, if the looting from them occured quite recently), then the memory problem doesn't seem so tricky anymore.