Whilst I sympathise there are plenty of people in the workplace including myself who do 10-12 hour shifts and only get a half hour break in the whole day. 6 hours with no break is something I do on a regular basis at work as I'm sure a lot of people do.
It is odd that you seem to be on one of the few courses that do this though, perhaps speak with your course lead about it? If you don't get anywhere in actually getting the lectures spread out more, bring food in with you and see if you can eat it during lectures?