The 4.0 is a very durable engine and can last decades and hundreds of thousands of miles when properly maintained. Your main problem with that vehicle is probably going to be electronics and emissions. Chrysler products are known for having weak electronics. The later 4.0 engines (yours is the next to last year) have dual pre-catalysts integral with the exhaust manifold, a main catalyst further downstream, and four O2 sensors to monitor the whole mess. When those components start to deteriorate it can get expensive to put right, and you are in a state that requires emission inspection.

Additionally be sure to maintain the cooling system and keep the coolant fresh. There are two core plugs in the back of the engine that are difficult to get to when they start to leak. There is one on back of the block which requires the transmission be dropped to get to it. There is also one on back of the cylinder head that at least on the old Cherokees is inaccessible without doing the same (or pulling the head). Normally when one starts leaking you do both.

The heater cores and AC evaporators on Jeeps are notoriously weak. On the Cherokee complete dash removal is required and once again if one goes common practice is to change both. Not sure if it's the same situation on the Wrangler.

Since you have a manual trans you thankfully don't have to worry about automatic transmission problems.

Play the lottery frequently as this vehicle is going to become very expensive, very quickly.