You are right, the USB is the fastest method for syncing and converting process. And you are also right that conversion is rather consuming process, however it should not take so much time. In order to troubleshoot this question, try selecting the "Activity log" plugin, from "More options" area, before pressing "Sync Now" button in SyncMate. This way you will see the actual software activity in the real time, while it performs the conversion and syncing. Thus, in case if it hangs or fails, you will see the actual problem in the log.
Please, try this, and let us know the result.