* For my country table, I used the
country code as the primary key "AU,
US, UK, FR" etc
* For my currency table, I used the currency code as the primary key "AUD, GBP, USD" etc

I think what I did is ok, but another developer wants me to change all the primary keys to an int, because the country code, currency code might change sometime in the future he said. We just don't know that, well in this case he is right, his path is the safest path to take.

Should I change the primary keys to an int to be safe rather than be sorry? Can't I just keep it?