There are few parameters to refresh UWL in portal.
UWL has to be refreshed very frequently so that the work items that are generated will be updated whenever we look at the UWL inbox of portal.
Open the UWL iview and fine the below properties
1) wait duration before calling provider on loading preview
2) wait duration before calling providers on loading of UWL
3) wait duration for UI refresh while waiting for update
Make sure you have minimum seconds for loading the UWL page. Check the below attachement for more detailed understanding.
Also please check other wiki for UWL delta pull mechanism.