Same happened here. After the upgrade Office showed 29 days remaining, now it shows 149!
Hmmm, noticed today that my Office 2016 Preview says there are updates available but when I click yes to download them in background, nothing happens. Yes, I know it's happening in the background, but I'm not new to this notion, but there's no process running in background! I've checked. Just doesn't seem interested in updating this week. I've done a quick-repair but no difference. Odd.
I figured it out. If I turn off metered connections under my wifi setting (I need it on as I have a internet cap during week) then it'll update ok. Must be a bug in the preview. I've sent description of issue in the feedback app as it should still download when metered connection on but only on demand.
So what's new in this 2016 edition?
It looks pretty much the same at first glance. Except there's a share button up in the corner now....
After installing RTM (Clean) I re-installed office 2016 again -- selected ENTER PRODUCT NUMBER for activation rather than Ms account -- now it expires after the FULL 120 days.
Use the key in the first post in the thread.
For IMAP you don't lose any email --for stuff saved locally just ensure you save the .pst file in your documents-->Outlook files before doing the clean install and copy back to your document folder again after installing Office 2016.
For POP3 save the .pst folder as described above. I actually can't see any value though in using POP3 when IMAP is available.
Office 2016 has much better Themes (I hate that HIDEOUS white in outlook 2013) and EXCEL / Powerpoint have some new features.
Outlook 2013 LOSES email too if you move it to user folders - Outlook 2016 much better all round - folders not hidden etc - but simply in documents-->outlook files.