I have the same experience. I don't have an exact way to produce it. I feel that saving with "Save as..." and loading with "Open recent home..." might be a reason. I'm closing all unused instances so only one is open.
Also I have seen that the java process needs more and more memory.
Starting with no home it is 180 MB, with the first home it is about 500 MB, with the second it is 680 MB, opening the first one again I'm at 900 MB.