I just installed Avast Free.
The subscription expires in 28 days on June 25, 2017.
What happens then? Does it automatically renew the free subscription?
Thanks for the help.
Why don’t you use the register button and register it for a year ???
I solved the problem.
I went to Add/Remove Programs >Avast >Change and I got an Avast Popup page that had an Activate Button to click to renew my free subscription. I now have 364 days remaining.
No such option if I do that as I still have 252 days remaining 
I wonder if that would work when you don’t have any internet access ???
It could work as it will auto register for a year if there is no Internet connection.
If that’s the case, it’s an easy fix for those without internet access and those currently not being able to register the free version. 
I think it worked for me because I had just installed Avast and only had 28 days remaining. I remember on the main Avast GUI page, at the lower left there was an Activation Button, but I didn’t know what it was for at the time. Now, that button has changed to an Upgrade Button.
I was connected to the internet when I did this.
Well, someone from avast said it will auto-register if there is no Internet connection when the 30 days are over.
Could very well be the same will happen if someone does the same as greyowl did.
He didn’t say auto register he simply said you would still be protected.
That is somewhat of a leap of faith, given greyowl’s comment “I got an Avast Popup page that had an Activate Button to click to renew my free subscription.”
That it could well require an internet connection to do that and possibly update your my.avast.com account.
I just did a clean install of the Free version of Avast and tried that Change option unfortunately there was NO offer to register the program.
I kept the computer OFF-LINE while doing this.
http://screencast-o-matic.com/screenshots/u/Lh/1495925600865-55180.png
To Activate and Register, you need to be on-line.