Caching Behavior in SOAP Web Services
Preferences, customizations, and custom fields are cached by SOAP web services sessions, both in CRUD and search operations. For example, if you enable or disable an accounting preference at Setup > Accounting > Preferences > Accounting Preferences (Administrator), your current SOAP web services session still retains the previous setting of the preference.
To make sure that your SOAP web services requests respect your updated preferences, customizations, and changes in custom fields, you should wait 60 minutes for the session timeout. After the timeout, the new SOAP web services session will respect the changes you made.