I am using EpPlus (version 3.1.3.0) and observed that, when I add a new worksheet to workbook with a name of 35 char, it trims the name to 31 char.
Do we have any newer version of EPPlus with the fix.
This is an apparently un(der)-documented limitation of Excel, not EPPlus (or even OOXML's SpreadsheetML, based on what I've gleaned from ECMA-376).
See this other SO answer.