BApp details: Session Timeout Test
This extension attempts to determine how long it takes for a session to timeout at the server. It issues the same request multiple times with increasing delays until a configured string appears in the response.
You can install BApps directly within Burp, via the BApp Store feature in the Burp Extender tool. You can also download them from here, for offline installation into Burp.
Please note that extensions are written by third party users of Burp, and PortSwigger Web Security makes no warranty about their quality or usefulness for any particular purpose.