No, it's not possible to increase this value. It's set as 5 minutes to guarantee that the latest utag files are always served when you do a publish.
Most of the time, the utag files will be served from cache anyway, and if the file has not changed, it will not be re-downloaded. The 5 minute expiration is simply a check to see if the file has changed, and it will only be re-downloaded if this is the case.
Hope this helps to explain things.
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