Packet loss & slow speeds

In the past week, during the late evenings (After 10PM), the speeds will drop dramatically, along with some high (40-50%) packet loss, and the high ping times that come with it. Sometimes this clears itself up, but others not. I've called before and they wanted to send a tech out, but since the issue had cleared up by the time they wanted to be here, I cancelled it. Now the issue is back, but won't be if someone is sent out. Is there something Comcast here can do to target this intermittent issue?