Overall goal: If a node has not been commented on in an in a given time frame, send an email.
How it could possibly be done: Have RulesRules look at the last time a comment was posted when cron runs. Then do a data comparison of that unit (current time - last comment posted time) to see if its greater than the time frame assigned to the node (ex: hours). If so, send email.
Is this approach correct? I am struggling to get the Rule to work if it is.