two questions about etags

[Luca Ferrari]

Hi all,
the first question is about the concurrency against the TAG file: I'm
thinking to place a cron job to automatically update the TAGS file at
regular intervals, what are drawbacks of this solution considering I
could be using the etags system in the meantime?
Second question: is there a good way to search for unused tags (e.g.,
functions not called anywhere)?

Thanks,
Luca