What research has been done that demonstrates the practical lifetime
of a "permanent cookie" on a browser?  That is, a cookie set to expire
in the year 2020 often doesn't last that long because often cookies
get deleted either manually or by third party applications.  How often
does this happen, and what is the practical lifetime of cookies?  I'm
looking for actual data performed on large data samples.

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Clarification of Question by jt_cookiemonster-ga on 07 Jul 2003 15:46 PDT

Companies that have distributed desktop software may be able to report on this.

I was thinking about this, but I am not sure how such research could
be performed. Afterall, once a cookie is removed, you don't really
know that. If the user visits again, then they will be given a new
cookie, you have no means of knowing they had a cookie and removed it
before.

Or a person could simply stop visiting. The best you could do it track
the set time and most recent read of all the cookies you had issues.
You'd then know the longest time that a single cookie had been
returning to your site.

With that in mind, I had a look, but couldn't find anything that
looked like the data you'd like. I have some sites I could look at
myself, but nothing that has been running long enough or with a large
enough userbase to give you anything like the information you want.

Good luck with your search, I'll keep an eye on your question to see
if anyone can find the numbers, it seems interesting.

Regards,
Sycophant-ga