Thanks to a nice forum posting over on the HowardForums, you can now cut that sync time down and still be prepared should something unfortunate happen to your iPhone that forces you to have it replaced.
The process is simple and it involves turning off the ability to send diagnostic data to Apple.
With just a few easy steps you should be left with sync times that are much more manageable, of course this will not help if you add a bunch of new media or the first sync after you add some new apps, however regular or routine syncing should be much more pleasant.
After connecting your iPhone to your computer
* 1. Uncheck the check mark from the “Automatically sync when this iPhone is connected” option in iTunes.
* 2. Unplug your iPhone and then plug it back in
* 3. Once iTunes launches again, right click on its name in the devices menu (on the left) and from menu choose “Reset Warnings”
* 4. Then click Sync in the bottom right hand corner
* 5. You will then receive a pop-up (see image below). Simply uncheck the “Do not ask me again” box
* 6. Now you can go back and re-apply the check to the “Automatically sync” option that you removed in Step #1 Source...