I would like to propose making Tumblerd shut down when not used for more than 30 minutes. Then automatically launch it when needed. This works around memory usage issues with long sessions. This, for example, helps people who only reboot their computers once a week when Mr. Greg Kroah-Hartman releases new stable kernels :)
It is already the case, the timeout is much less than 30 minutes. If you feel like tumblerd is not doing that (and that there is no other process asking tumbler for thumbnails, like Thunar), then please feel free to re-open.