Does anyone know how many miles the 3.6 Liter engines will typically run before needing a rebuild? How does the 3.6 compare to the 3.5 it replaced?

Totally different engines.

They have not been out long enought to know much about the reliability except they are better than the 2.7

I have a 2012 3.6 in the work vehicle, 118k miles on it with nothing more than routine maintenance. It still runs hard. Just a data point.

Not sure about the 3.6 engines yet except now that they have had their cylinder head issues identified, they should be good to go! They are a good running engine but so is the 3.5....

Just this week, we had an 09 Journey with a 3.5 come in for an emission issue and it had 464,000 miles on it. The only major repairs it had ever had done to it was the timing belt replaced twice and the transmission rebuilt once. Proper maintenance was done to this vehicle and it sounded great!!!

We have a lot of 3.6 engines in the Postal fleet and are doing very well.

How about the 5 speed trans that is behind it? I have a '13 Durango lease and I'm up in the air about buying it out or going into a '16. The '13 is awesome and hasn't needed anything but maintenance. But that's only with 44k miles on it.