The 3.5L has a 100,000-mile tune-up interval, thanks to its NGK platinum tipped spark plugs. And from what I've read the timing belt is good for 105K. Judging from my experience (and the experience my family has had with Chrysler products), Chrysler engines tend to be very durable and long-lived.

Having driven a recent Pacifica and numerous LH cars with this exact same engine in them, I have to say that the 3.5L is also quiet and well-mannered. It's a world class engine in every respect. However, it doesn't get the attention it deserves from the motoring press because Chrysler tends to always put it in heavier cars. But it is worth remembering that when the magazines are praising the 240-250 hp V6 engines found in the Nissan Altima 3.5L, Honda Accord V6, etc, Chrysler has been building something competitive for years.