I'm from a Jeep family. My dad owned a 1987 Cherokee that we put about 220,000 miles on before we sold it. I think he rebuilt the engine around 150,000, and had to replace a few radiators due to deer encounters.
The next Jeep was a 97 Wrangler that we built up for off-roading. Because it's a toy it ended up sitting for a year or so, and afterward needed some fuel system work, but other than that runs just fine.
He also had a 99 Grand Cherokee (which replaced the 87 Cherokee). Also no major problems, although I'm not a fan of the way this model Grand Cherokee handled.
It was replaced with an 05 Grand Cherokee which handles much more nicely in my opinion and is still running.
My Jeep was an 03 Wrangler that we built up for off-roading, and in doing so ruined it. The suspension we put on was made in California where apparently they've never heard of rust. It was my daily driver in Ohio, and after the first winter most of the undercarriage was rusted together. I can't remember the last time I changed a part under it without having to drill out a bolt. My brother drives it daily now.
Before that, he drove an 02 Cherokee that, again, we ruined with a suspension lift. He wrecked it on the road and insurance totaled it.
Another brother has a 99 Wrangler that he bought already modified, which never sees salt, and is in great condition. He had a few problems with an after-market computer chip, but other than that all the repairs he's made have been due to unfortunate encounters with terrain.
So, in my experience the 4.0L engine is fairly bulletproof, and if you can avoid screwing up the suspension lift they are excellent machines for local driving and off-roading.