I've had mine for 15 years and do not plan to change anytime soon. 175K miles, V8, 4x4, never let me down. I'd like to get to 250K.
The only thing that would cause a change is a 6th gen 4Runner ... if the new model looks like an upgrade I might buy one to get another 15+ years of trouble-free motoring and light off-roading. But if I don't like it, then I'd feel compelled to buy one of the last of the 5th gens. But with no 6th gen in sight, keep on driving the 4th gen forever.
You can aim higher than that lol...I just cracked 250k this month and she's got no signs of slowing down (even after I neglected it big-time as a college student). Owned mine for 10, second owner though. A few grumbles here and there that I need to take care of but it's been stupid cold out until recently which makes them louder.