In the past, I have observed a problem where after playing for some time, the game starts lagging, resulting in lower framerates and choppy sound. While restarting the game always made the problem go away, I also noticed that the problems did not happen if I turned off all the non-essential services on my computer. By process of elimination, I found that the culprit was actually ntpd, the service that synchronizes the clock to a remote server. I disabled that service and update the time manually from time to time, and I have never seen that issue since.