Couple of points... Firstly this is really a software question but you posted this in General Hardware
But seriously, I think you may be approaching this from the wrong angle. Whilst you could write a script to easily check the age of files on a USB stick and delete any older than
X days, and you should be able to have the script run if Windows notices a new device being connected... but that seems a ball ache to me.
Instead, what I would do, is to define a Data Retention Policy that covers removable media, and which all employees are required to agree to. State a maximum age based on security classification, e.g. C1 / Unclassified, C2 / Restricted, C3 / Confidential, C4 / Top Secret.
Next, tell your staff that you will be randomly performing audits to ensure people are adhering to the Data Retention policy and that any persistent non-compliance will leave them open to possible disciplinary actions. The onus is then on them to make sure they're performing housekeeping.
Lastly, if you're not already doing so, you really should consider encrypting your USB sticks - there are loads of different products to do this, ranging in price from free to very expensive depending upon the features you need. In this way, even if a user's USB key does contain old versions of files and it gets into the wrong hands, then you don't care because they won't be able to read the data.
