Is there a way to configure devices that are not responding for some period of time to be removed from Spectrum automatically?
Any version of Spectrum
You can perform this action through "Contact lost Model Destruction" and "Destruction delay(sec)". These settings can be found on the VNM Model, located in the Universe View. Simply highlight the VNM icon and go to it's Component Details view. Expand the Fault Isolation folder in the Component Details view and there you will see the Contact Lost Model Destruction and Destruction Delay options.
Here you can customize the Destruction delay in seconds. The default value 604800 seconds which is equivalent to 7 days. If you want to increase the value you can do it through updating the value in Destruction Delay field which is under Component Detail ->Information ->Fault isolation option.
After setting the value you need to set the "Contact Lost Model Destruction " to Enabled.
Take note that this setting only applies to models that lost connectivity after you change the setting. For example, if you have 5 devices that have been down for 30 days and you set the model destruction for 20 days, those models will not be destroyed. You will need to destroy them manually. Any new models that are then down for 20 days after you make the change will be automatically destroyed by Spectrum.