After meeting the IE killing add-in problem as per https://feedback.avast.com/responses/internet-explorer-and-avast-online-security I’m wondering itf it’s now OK to update the browser add-ins. Met the problem a month ago and also last week on separate machines that were fully up to date…
That link is a month old. Since then avast has had two release refreshes.
Most issues seem to be with IE 11. That said, the main issue involves the
“avast online security”. That said, you can disable the AOS within IE by clicking
on “tools” (the sprocket/gear). 
Short answer…yes you will be fine.
“Met the problem a month ago and also last week”
Will try again, last week was on current refresh…
Try disabling the AOS in IE 11.
You can revert back to Avast 8 and have a working Avast. Or you can use another AV solution that works without having to disable parts of your AV.
When my IE version was IE10 my Avast Free version was 2014.9.0.2007 I had a problem with my Avast Online Security causing slow loading of homepage google. I then reported this issue to Avast Support and submitted a ticket and I submitted some log files via Avast GUI. When Avast made an update to 2014.9.0.2008 and I still had IE10 all of the issues were gone. When Microsoft released IE11, Avast Online Security and IE11 works fine.
I did a complete and clean reinstall of Avast 2014 Free Edition.