The time each sync takes depends on a number of factors.
For example, syncing may take longer the very first time you sync, after you’ve added a new device to iSync, or if you’ve turned off syncing for a particular type of information (such as your calendars) and then turned it back on.
In these cases, iSync must analyze all your information, then compare the information on all devices, which may take a while. After that, iSync will “remember” the information it synced the last time, and subsequent syncs will take less time.