Script Dependencies

Ok so this is the issue i am faced with i have approximately 5 directories containing thousands of scripts. I'm trying to identify all the scripts that are obsolete or have not been run in a while. I can traverse the crontab and get the main scripts and their dependencies from that and then traverse the script with python and regular expression to find the dependencies. The problem exists is for the on demand scripts or scripts that aren't in the crontab how would you find which ones those were? I'm more so looking for ideas on how to tell when a script was ran last. Normally you could scan output but not everything has output which is causing this problem. We are running RHEL 5 so any ideas on how to do this would be great.

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