Google Contacts, eTags, Updated changing on every access - google-contacts-api

Question

I am trying to use the eTag from a call to get Google Contacts. Since there is an eTag on the "top level", I was hoping that I could check it to determine if anything in the contacts dataset had changed. Here is my request:
Request URL: https://www.google.com/m8/feeds/contacts/default/full/?max-results=0
Request headers:
Authorization: Bearer
Depth: 1
GData-Version: 3.0
Content-Type: text/xml
My thought is that if I request for 0 results, I'll have just the information I need. I can check the eTag against the one that I stored, and if there is no change, there were no changes to any contacts. The XML I get back:
<?xml version="1.0" encoding="UTF-8"?>
<feed gd:etag=""QXYyfzVSLyt7I2A9XRRQFkwJRAA."" xmlns="http://www.w3.org/2005/Atom" xmlns:batch="http://schemas.google.com/gdata/batch" xmlns:gContact="http://schemas.google.com/contact/2008" xmlns:gd="http://schemas.google.com/g/2005" xmlns:openSearch="http://a9.com/-/spec/opensearch/1.1/">
<id><email address here></id>
<updated>2015-02-11T00:09:00.897Z</updated>
<category scheme="http://schemas.google.com/g/2005#kind" term="http://schemas.google.com/contact/2008#contact"/>
<title>Joe's Contacts</title>
<link rel="alternate" type="text/html" href="https://www.google.com/"/>
<link rel="http://schemas.google.com/g/2005#feed" type="application/atom+xml" href="https://www.google.com/m8/feeds/contacts/joe%40ihouseweb.com/full"/>
<link rel="http://schemas.google.com/g/2005#post" type="application/atom+xml" href="https://www.google.com/m8/feeds/contacts/joe%40ihouseweb.com/full"/>
<link rel="http://schemas.google.com/g/2005#batch" type="application/atom+xml" href="https://www.google.com/m8/feeds/contacts/joe%40ihouseweb.com/full/batch"/>
<link rel="self" type="application/atom+xml" href="https://www.google.com/m8/feeds/contacts/joe%40ihouseweb.com/full?max-results=0"/>
<link rel="next" type="application/atom+xml" href="https://www.google.com/m8/feeds/contacts/joe%40ihouseweb.com/full?max-results=0&start-index=1"/>
<author>
<name>Joe</name>
<email>joe#ihouseweb.com</email>
</author>
<generator version="1.0" uri="http://www.google.com/m8/feeds">Contacts</generator>
<openSearch:totalResults>42</openSearch:totalResults>
<openSearch:startIndex>1</openSearch:startIndex>
<openSearch:itemsPerPage>0</openSearch:itemsPerPage>
</feed>
Everything looks good.. except that each time I make the call, the updated date and the eTag come back different. I can make 10 calls in a row, and each time the eTag is different. Is this not a valid way to use the API? If the eTag comes back different every time for anything, then I can't use it to determine if something has changed. Isn't that what the eTag is for?
andy
Here is a sample - I am making the request above 10 times, at 5 second intervals. This is my personal account, so I'm pretty sure that no-one is changing any values on me. Note that the eTag and "updated" values are different each time. The first column is the time I made the request (PST), the second and third are the resultant eTags and updated values.
16:38:30 : "SHYyfTVSLyt7I2A9XRRQGEoORAQ." : 2015-02-14T00:38:29.895Z
16:38:36 : "RHY-fjVSLyt7I2A9XRRQGEoORAU." : 2015-02-14T00:38:35.856Z
16:38:42 : "QHk9ezVSLyt7I2A9XRRQGEoORAY." : 2015-02-14T00:38:41.763Z
16:38:47 : "Rns6cTVSLyt7I2A9XRRQGEoORAY." : 2015-02-14T00:38:47.519Z
16:38:53 : "Qnw-fzVSLyt7I2A9XRRQGEoORAc." : 2015-02-14T00:38:53.257Z
16:38:59 : "SXc5ezVSLyt7I2A9XRRQGEoORAc." : 2015-02-14T00:38:58.923Z
16:39:05 : "RXg5ezVSLyt7I2A9XRRQGEoORAA." : 2015-02-14T00:39:04.623Z
16:39:10 : "QX06cTVSLyt7I2A9XRRQGEoORAE." : 2015-02-14T00:39:10.319Z
16:39:16 : "R346eDVSLyt7I2A9XRRQGEoORAE." : 2015-02-14T00:39:16.010Z
16:39:22 : "QHgyfjVSLyt7I2A9XRRQGEoORAI." : 2015-02-14T00:39:21.696Z