This is a very useful tool. Thank you. I have a suggestion.
What I usually do is:
1.) clean project
2.) zip
3.) rename with a time stamp e.g. project_2013.02.20_01
4.) copy to dropbox. If the filename already exists I rename it to e.g. project_2013.02.20_02
With TreeTrim it does the first two parts. It would be convenient if it did all four. I guess I could write a batch script for this but maybe it could be easily to integrate into TreeTrim.