I just uninstalled Avast, and I'm happier for it.

Now, I have a 3 PC Premium license with over 500 days left on it.

Is it Refundable?

Why did remove it?

The short answer:
I like a PC I can use.

The slightly longer one is best said in numbers.

Android Studio startup:

  • With Avast: ~4 minutes
  • Without Avast: ~2 minutes

Android Studio APK build:

  • With Avast: 3-4 minutes
  • Without Avast: 1-1.5 minutes

Media Playback:

  • With Avast: frequent audio stutter, and DPC queue latency spikes in excess of 65ms. Video frame drops. Even when the machine is otherwise idle.
  • Without Avast: I ran a Linux (Ubuntu) Distro upgrade in a VirtualBox using 2 of my 4 cores, full system scan in Spybot and MS Security Essentials, while working in Android Studio with an Eclipse instance in the background, playing music from Google Music.
    4 hours with the CPU hovering at about 90%, and not a single problem with media playback, not one jitter.

Daily use:

  • With Avast: Randomly and rather frequently the Avast Service would start the “smart scan” and use 25-30% of my CPU. That it goes above 25% means it is trying to use more than one core, but can’t. The DPC queue spikes to the aforementioned 65ms (average) and the UI stops.
    The mouse pointer moves like a limp tortoise wading through molasses. Avast has no business doing anything on the DPC queue beyond updating its UI, but sadly I see software using it to gain a few extra percent performance, and as a result ruins everything else.
  • Without Avast: No problems at all. The system is as snappy and responsive as the day I installed it (including an older version of Avast)

Avast 2015 is their Vista, but unlike MS, they don’t seem to acknowledge the problems. Instead every new update went from bad to worse.

The longer version:
Self censored due to appropriate language

You could try the latest Beta/RC: https://forum.avast.com/index.php?board=15.0

Now, I have a 3 PC Premium license with over 500 days left on it.

Is it Refundable?

First I’m an avast user like yourself, so I can’t speak for avast software.

I don’t believe it would be refundable, refunds are permitted in the first 30 days of use. Given you have 500 days left it would appear you have been using it for more than 30 days. That said I don’t know if you might be able to get a refund on the unused year.

You could try the avast 2016 beta RC2 version as suggested.

You could also try submitting a support ticket requesting a refund (of the unused year), not sure how much luck you might have with this.
Try the following: https://support.avast.com/support/tickets/new.