According to the provided information, I suppose that you are using the GridViewSpreadExport: https://docs.telerik.com/devtools/winforms/controls/gridview/exporting-data/spread-export
It utilizes our RadSpreadProcessing library to export the content of RadGridView to xlsx, csv, pdf and txt formats: https://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/overview
However, there is no strict limit for the number of sheets: "Sheets in a workbook - Limited by available memory (default is 1 sheet)"
Considering the fact that some of the grids may have 100K rows, I would highly encourage you to try the GridViewSpreadStreamExport. It allows you to create big documents (without loading the entire document in the memory) and export them to the most common formats. Additional information is available in the following help article: https://docs.telerik.com/devtools/winforms/controls/gridview/exporting-data/spreadstream-export
I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Dess | Tech Support Engineer, Sr.
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