If you get a new Mac, and want to migrate all your Time Sink data to the new machine, you need to worry about one file and one folder. The file is Time Sink's preferences, stored here:

/Users → you → Library → Preferences → com.manytricks.TimeSinkClient.plist

And the folder you need — because this is where Time Sink's history resides — is here:

/Users → you → Library → Time Sink

Move those two items to the same spot on your new Mac, and you'll be set. (Remember Apple stupidly hides your own Library folder, so you'll need to hold down the Option key when selecting the Go menu in Finder to see it.)