Caching Behavior in SOAP Web Services
SOAP web services sessions cache preferences, customizations, and custom fields, both in CRUD and search operations. For instance, changing an accounting preference at Setup > Accounting > Preferences > Accounting Preferences (Administrator) won't immediately update the current SOAP session.
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 session will reflect your changes.