I want to purchase a used Jeep Wrangler. Any advice on maximum age or mileage I should consider.

Look out for the infamous death wobble.

The single best thing about a Wrangler, in my opinion, is that, if you're willing to work on them, they will run forever. Every single part on them is available - it is literally possible to build one from scratch. That being said, I would be cautious about buying a 4cyl due to the fact that they are generally underpowered and have likely been run harder to keep up. But, if you get a good deal on one, buy it, yank that engine out and plop in a V-8 or a 4bt diesel. The sky's the limit!

Remember "J" stands for junk. Pick another brand.

..great vehicles if you have kidney stones..