When running a Constituent export, some users may find that an export that took a few minutes to run in the past ends up taking several hours to run. A significant portion of the export is taken up by Summary Information fields.
We are currently evaluating this issue and will update this article when we have more information.
Alternative solution: Do one of the following: 1. Break the query down that is being used in the export into smaller sections so the export has less constituents to run. 2. Have two exports. One with the Summary information and one with the rest of the export and combine them in the excel afterwards. 3. Allow the export to continue to run.