Hi!
Thank you for Source tree! It's best git gui for me. But sometimes happens memoty leaks issues. Usally Source tree use just about 70-250mb, but sometimes, without any visible reason it starts use more and more memory until all available memory ends. It's happening not only with me, but with many of my collegues. And the only way to stop it is restart source tree. By the way, previous versions had the same issue.
For example, my platform is win7, 6gb DDR. I have only one quite big git repo (100000 files) with few branches (about 2-4 branches) and a lots of branches in remote.