Anyhow, importantly, every time they release a new version, they've been able to improve not only GUI features but PC resourced related features such as memory and CPU usages, and with this latest v206, according to the developers, Kupfer now runs faster than ever! but uses 10-30% less memory nonetheless.
If you use the PPA for Kupfer in Ubuntu then you must have the latest version, but for those who haven't yet installed it, you can do so by entering the below command in your Terminal.
sudo apt-add-repository ppa:kupfer-team/ppa
sudo apt-get update
sudo apt-get install Kupfer