It might slow things down slightly. I don't know of any side-by-side comparisons of server load.
Do the back of the envelope calculation. 30 students, autosave every minute (assuming you choose the highest frequency). That is only one request every 2 seconds, which is not much. (Well, I have just been load-testing the OU system with an average load of 30 requests per second, so it does not seem like a lot to me.)