Using Genymotion Desktop for a long period of time causes memory leaks which renders Genymotion extremely slow and unstable.
This is a known limitation with Genymotion Desktop and no fixes could be implemented so far.
Due to this, Genymotion Desktop is not suitable for automated, scale tests or any other use case which requires to run more than one virtual device for more than 8 hours.
However, we have specifically designed our Cloud products for such usage. For more information about our Cloud offers, feel free to visit https://www.genymotion.com/