@Bill Dalton The most problematic issue when you regenerate a large number of images as you say you have is not having a sense of control and completion of the task (because of errors / timeouts etc.). In case you have a consistent method of regenerating those images without the "fear" of timeout of failure - your issue should not longer be a problem - my point being that the core of your problem (and others) is consistency and not speed (eg. you could leave a regenerating task to run for 1,2,3 days as long as you know the process will complete and do the job consistently for you).
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@Bill Dalton The most problematic issue when you regenerate a large number of images as you say you have is not having a sense of control and completion of the task (because of errors / timeouts etc.). In case you have a consistent method of regenerating those images without the "fear" of timeout of failure - your issue should not longer be a problem - my point being that the core of your problem (and others) is consistency and not speed (eg. you could leave the task to run for 1,2,3 days as long as you know the process will complete and do the job consistently for you).