What can I do to help the longevity of my Jeep?

Change all fluids with new: oil, tranny (filter too), brakes, difs and transfer case, wouldn't hurt to flush out the radiator. Pull the EGR valve and clean it or just replace. Also fuel filter. Speedometers are known to go out on these things with more miles, so you may keep in mind to be on the look out for one at a wrecking yard. Is it a ZJ or other chassis year? ...oh and of course have the brakes and tires inspected. Even though some still have plenty of tread left if the tire is many years old the heat from driving and from the road surface can literally melt them and you'll have a blow out.