What to do with old SIMS if revisiting same country years apart?

[Przemolog]

Originally Posted by fedeprovenza

If the sim expire you can't use it anymore

And it doesn't have to be the operator's bad will not to bring such a dead SIM back to life. If the SIM has been dead long enough, the number may have been "recycled" and sold to another user, and later even ported to another network.