I'm not sure if this specific bug is reproducable or if it actually has something to do with the current minecraft version or my pc or anything else, but I randomly noticed, that Minecraft apparently doesn't clear memory any more in the latest snapshot (or couple of snapshots ago, idk). This is the first time I've realized this. Just wanted to mention this in case it IS a major issue.
I'm playing on GTX 760, 16GB RAM, whereof 10GB are assigned to Minecraft in the launchers start parameters.