Are orcs immortal??

[pandora]

we don't seem to hear about Mrs. Orc.

Perhaps for the same reason we don't hear much about Mrs Dwarf.

How can you be immortal but only until the end of the first age?

I meant that, once Morgoth is out of the picture the spirits of the dead only have the option to repent or drift away; there is no longer a Valar prepared to summon them to new bodies. I didn't mean that they dropped down dead at the end of the age; just that they might no longer get "extra goes" if they are killed. Unless Sauron could do the re-housing trick which perhaps he could given his title of Necromancer.