Osna makes a very interesting point in bringing up technology. I personally don't look for the latest and most advanced tech applications on cars, they're not on my values list(key in decision making for all, this must not be ignored), though I find them intriguing. I look to technologies that increase performance capabilities, technologies that are normally std. fare. At the end of the day, we all buy cars to get us from point A to point B, how we get between those two ponits, well, that's where our value system comes in.
As far as how long I believe a car should be kept? 6 yrs. minimum, this frame of time allows you to keep up until a referesh of a next generation model, or to just stay "current" in the general sense. Maximum is ten years, the tenth year is somewhat past the critical period in the running of the car and anyones guess as to what might happen as far as reliability.