With SSL VPN in XG Firewall, you will be disconnected, NO MATTER WHAT, efter 8 hours, this is default. Even if your are transfering data you will be kicked off 🙂
This can be changed, by modifying this parameter in XG:
Here changed to 10 hours = 36000secs:
After that, press APPLY and all new connections will timeout after 10hours now 🙂
Please, also pay attention to the “Disconnect dead peer after” and “Disconnect idle peer after” parameters, so it’s not them, who is causing the issues 😉