Timeout after 30 seconds when executing package via .NET

Case
I'm executing a package via .NET (example 1, example 2), but if the packages takes more than 30 seconds I get an error: Timeout expired.  The timeout period elapsed prior to completion of the operation or the server is not responding. Changing the timeout in the connection string to for example 300 has no effect.

// C# Code (incorrect)
// Connection to the database server where the packages are located
using (SqlConnection ssisConnection = new SqlConnection("Data Source=.;Initial Catalog=master;Integrated Security=SSPI;Connection Timeout=300")
{
  try
  {
    // SSIS server object with connection
    IntegrationServices ssisServer = new IntegrationServices(ssisConnection);
    
    // The reference to the package which you want to execute
    PackageInfo ssisPackage = ssisServer.Catalogs["SSISDB"].Folders["SSISJoost"].Projects["MyProject"].Packages["MyPackage.dtsx"];

    // Add execution parameter to override the default asynchronized execution. If you leave this out the package is executed asynchronized
    Collection<PackageInfo.ExecutionValueParameterSet> executionParameter = new Collection<PackageInfo.ExecutionValueParameterSet>();
    executionParameter.Add(new PackageInfo.ExecutionValueParameterSet { ObjectType = 50, ParameterName = "SYNCHRONIZED", ParameterValue = 1 });

    // Add a package parameter
    executionParameter.Add(new PackageInfo.ExecutionValueParameterSet { ObjectType = 30, ParameterName = "myStringParam", ParameterValue = "some value" });

    // Get the identifier of the execution to get the log
    long executionIdentifier = ssisPackage.Execute(false, null, executionParameter);
  }
  catch (exception ex)
  {
    // Log code for exceptions
  }
}

Solution
The 30 seconds is the default timeout which apparently can't be changed in the ssisPackage.Execute command. The solution is a little dirty. First remove the SYNCHRONIZED parameter to execute the package asynchronized. Then add some code after the ssisPackage.Execute command.

// C# Code (correct)
using (SqlConnection ssisConnection = new SqlConnection("Data Source=.;Initial Catalog=master;Integrated Security=SSPI;"))
{
  try
  {
    // SSIS server object with connection
    IntegrationServices ssisServer = new IntegrationServices(ssisConnection);
    
    // The reference to the package which you want to execute
    PackageInfo ssisPackage = ssisServer.Catalogs["SSISDB"].Folders["SSISJoost"].Projects["MyProject"].Packages["MyPackage.dtsx"];

    // Add execution parameter to override the default asynchronized execution. If you leave this out the package is executed asynchronized
    Collection<PackageInfo.ExecutionValueParameterSet> executionParameter = new Collection<PackageInfo.ExecutionValueParameterSet>();
    //executionParameter.Add(new PackageInfo.ExecutionValueParameterSet { ObjectType = 50, ParameterName = "SYNCHRONIZED", ParameterValue = 1 });

    // Add a package parameter
    executionParameter.Add(new PackageInfo.ExecutionValueParameterSet { ObjectType = 30, ParameterName = "myStringParam", ParameterValue = "some value" });

    // Get the identifier of the execution to get the log
    long executionIdentifier = ssisPackage.Execute(false, null, executionParameter);

    // Get execution details with the executionIdentifier from the previous step
    ExecutionOperation executionOperation = ssisServer.Catalogs["SSISDB"].Executions[executionIdentifier];

    // Workaround for 30 second timeout:
    // Loop while the execution is not completed
    while (!(executionOperation.Completed))
    {
      // Refresh execution info
      executionOperation.Refresh();
   
      // Wait 5 seconds before refreshing (we don't want to stress the server)
      System.Threading.Thread.Sleep(5000);
    }
  }
  catch (exception ex)
  {
    // Log code for exceptions
  }
}

Thanks to SequelMate and HansAnderss