So last night was my 5th game using the Google+ integration as we find that TokBox lags too much. At some point in every game, we all have to restart Hangouts, not because Hangouts is slowing down, but because Roll20 starts to lag. We can tell because the video seems fine and when we use the Google Hangouts chat, the chatting is quite responsive.
During this slow down, Pings will stop working, Page switching takes forever, and the chat window stops working all together.