To change application timeout:
cli/configure
ssh: set applications application junos-ssh inactivity-timeout 1440
telnet: set applications application junos-telnet inactivity-timeout 1440
web: set system services web-management session idle-timeout 1440

Note: auto complete does not work after application, so you will have to type it all in.

To view timeout settings, exit to cli
start shell user root
vty fwdd
show usp app-def tcp

And you’re done.