I've seen this advice from MMM as well, and just to provide a counterpoint, the last couple of manual transmission cars we bought needed one and two clutch replacements respectively in the time we owned them, about 14 years each, for close to $600 each. None of the automatic transmission cars we've bought have ever needed a transmission rebuild in the same amounts of time, roughly 160 thousand miles.
If you have to replace clutches more than automatic transmissions, then you're either 1)buying pre-abused cars with clutches that are already quite worn or 2) you're not driving it right.
We bought the cars new, we like to make sure we know the history of a car and maintain it to keep it reliable, so they weren't pre-abused. It is certainly possible that we didn't drive them right, though I don't think either of us was a particularly aggressive driver (at least until we more recently moved to New Jersey, sigh).
Perhaps it had to do with living in a very hilly, snowy area, quite a bit of shifting is needed on hilly roads going uphill on sharp turns. I think we did the 2-clutch car at about 80,000 mile intervals, which according to this (
http://auto.howstuffworks.com/under-the-hood/car-part-longevity/clutch-last.htm), is not unreasonable, they seem to think that 50k is not unusual, and getting over 125k is well above average, congratulations on your 170k!