On my 02 TJ, I added the SYE from the get go to eliminate any potential problems later (4.5 RE Long arm kit). On my 04 Unlimited, I just went ahead and added an Atlas (Custom 3 link in front with coil overs and bump stops, 4 link in rear).
IMO, your going to need it, so you might as well do it form the start instead of doing it later. One other aspect of the SYE to consider is that with it, you can remove the rear drive shaft and still limp home (Front wheel drive). You can't do that without the SYE kit.