I just noticed that the header for this topic mentions 4-Series, so this might not apply exactly.
I had this ¡°debugger time out¡± concern when working with my CP3 on my test bench. TB pointed me to this area to make the adjustment:
Open Toolbox, then Device Discovery, connect to the processor, select the FUNCTIONS button, select Authentication, then select Authentication Options. There is a box on that page to specify the ¡°Default User Idle Time¡±; set as desired or select NO IDLE LIMIT (my choice).
Please advise if this helps or applies to the ?4 series ,as I have not used one of those so far.