Most guys pocketbooks preclude them from changing stuff out before its time. I'd recommend you do the same; it just makes sense on an economic basis. Most of the problems with the XJ won't leave you on the side of the road. Fix it when it becomes symptomatic.
As for sensors, the one that is a very common failure on the 4.0 is the crankshaft position sensor. "Some" guys replace it strictly as a preventive measure and keep the old one as a spare. They are kind of a PITA to replace, especially on the side of the road or on the trail.
Best recommendation for longevity? Replace ALL fluids regularly. Coolant, oil, tranny, differentials. I see guys go nuts all the time with mods, etc and they still have their original tranny fluid in there at 75k. Fluids are the lifeblood of your XJ.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!