Clarification on usage of Serially Reusable Pragma for Oracle 10g

I need to make packages for Oracle 10g that can be changed while users are still logged in an using an application that makes database calls through PL/SQL. Unfortunately, anytime a package is updated while users are using it they get the following error:

ORA-04068: existing state of packages has been discarded

This makes it really difficult to make changes that are still compatible with the application that is using these PL/SQL packages.

I read that by using PRAGMA SERIALLY_REUSABLE the ORA-04068 error can be avoided.

After reading through lots of documentation, I keep stumbling upon the same warning for using the SERIALLY_REUSABLE pragma.

Serially reusable packages cannot be accessed from database triggers or other PL/SQL subprograms that are called from SQL statements.

The second half of this warning or other PL/SQL subprograms that are called from SQL statements is difficult to understand and I have not been able to find any examples through the Oracle website, Ask Tom, dba-oracle.com or any other website that provides information about Oracle products.

Question:

What are some examples for invalid usage of packages that implement the SERIALLY_REUSABLE pragma and will I be able to use this with client-side reference cursors?

Example Package 1

CREATE OR REPLACE PACKAGE example_package_1 AS
    PRAGMA SERIALLY_REUSABLE;

    FUNCTION get_database_system_time(
        date_time_format IN VARCHAR
    ) RETURN VARCHAR;

END example_package_1;
/
CREATE OR REPLACE PACKAGE BODY example_package_1 AS
    PRAGMA SERIALLY_REUSABLE;

    --------------------------------------------------------
    -- example 1
    --------------------------------------------------------
    FUNCTION get_database_system_time(
        date_time_format IN VARCHAR
    ) RETURN VARCHAR AS return_value VARCHAR(256);
        formatted_system_time VARCHAR(64);
    BEGIN
        SELECT
            TO_CHAR(sysdate, date_time_format) INTO formatted_system_time
        FROM
            dual
        ;

        RETURN formatted_system_time;
    END get_database_system_time;
END example_package_1;

Example Package 2

CREATE OR REPLACE PACKAGE example_package_2 AS
    PRAGMA SERIALLY_REUSABLE;

    FUNCTION get_time(
        locale IN VARCHAR
    ) RETURN VARCHAR;
END example_package_2;
/
CREATE OR REPLACE PACKAGE BODY example_package_2 AS
    PRAGMA SERIALLY_REUSABLE;
    --------------------------------------------------------
    -- example 2
    --------------------------------------------------------
    FUNCTION get_time(
        locale IN VARCHAR
    ) RETURN VARCHAR AS return_value VARCHAR(256);
        formatted_time VARCHAR(64);
    BEGIN
        IF locale IS NOT NULL THEN
            formatted_time := example_package_1.get_database_system_time('HH24:MI:SS');
        END IF;

        RETURN formatted_time;
    END get_time;
END example_package_2;