Currency Code with more than 3 characters

Hello, 

In Bookshelf (Setting up Currencies) Currency code is 'A three-letter code for the currency.' But on table S_CURCY, column CURCY_CD is defined as Varchar (20), in Quote Business Component Currency Code is defined as DTYPE_TEXT (20), from view Administration - Data / Currencies I can set a currency with more than 3 characters.

My question is  : Can we use Custom Currency with more than 3 characters without problem ? Do we use in your application Currency with more than 3 characters ?

Regards 

Jean-Marc