When I and some others first started with CPDN tasks were downloaded over dial up connections, the computers they ran on only had a single core and the tasks would last nine months on what for the day was a fast machine. That meant a lot of computing time could be lost if a machine crashed taking the task with it. So some of us would back up our work as insurance against that. In my experience about half of tasks restarted from a backup went on to complete successfully. The method of backing up used then was relatively simple as it only involved one task. Restoring one or two tasks out of say eight is a much more complex affair involving editing of client_state.xml and isn't worth the bother.

I will suggest to Andy that the bit in the FAQ about making backups is removed!