After starting a session to a remote system using Putty as a service, it may hang after one hour, even though the Applet Inactivity period and the Session Timeout Period have been set to 0 (unlimited, and in practice 48h)
This may be caused by the Max minutes before rekey value in the Putty settings. By default this is 60 minutes, and it specifies the amount of time that is allowed to elapse before a rekey is initiated.
If this is set to zero, PuTTY will not rekey
There have been issues reported in PAM and other products of ssh connections through Putty dropping after the amount of time specified for this parameter has elapsed
CA PAM, multiple versions
Change Max minutes before rekey to zero in your locally installed Putty