I think they would wear out after about ~100k. My Father had a GX with the 4.7 and his wore out right at 100000, as did my Mom's at a slightly higher mileage. I think (?) that the 4Runners equipped with the V8 had the exact same engine as the GX 470's.
I thought that the 4.7 V8's had the infamous timing belt problems. I don't think you need to change a timing chain unless it needs it (hence why they switched back to a chain) because they are more durable. Or I could just be an idiot (very real possibility). Also, change the oil every ~5k ish.
Off topic! It is almost just sad watching them nowadays. They used to own the Big 8, and dang, they went 60-3 from '93-'98? Holy cow?! Some of those players won more national championships than lost games. What the heck happened? I would love to see them do good again. Maybe their new coach can...
I had the same problem in my '05 Tacoma. I took it to the dealership, they replaced my U-joints and the problem went away for a few months, and then it came back. But after a few more months, it kinda just went away. If I were you I would take it to the dealership and see what they think. Hope...