The Taurus and most other cars are past the end of the design life at 100,000. You can expect quite a few parts to be wearing out and needing replacement. On domestic vehicles the length of the warranty is a good indication of the design life of the car. But for some brands like Honda that actually have shorter warranty periods than the domestics, the design life seems to be longer than the warranty period.
Considering how low of a price you can buy a used Taurus for, it can makes sense to look for one with lower mileage. Just try to get one with the Duratec V6 and AX4N transmission as it is more reliable than the Vulcan/AX4S combination. I think the Vulcan mainly ended up in rental cars.
I have never heard what caused the bad springs but my guess is bad heat treatments during manufacturing.
My parents bought a 1997 Mercury Sable station wagon with the Vulcan 3.0 in 2001, with about 50,000 miles. It now has 190,000 miles on it and is still their daily driver.
It has only needed spark plugs replaced, air filters, oil changes, and the transmission fluid and filter changed, when the shifting got erratic around 150,000 miles. That solved the problem. It also had the no-heat issue, but flushing out the cooling system solved that.
It proved to be such a reliable car that it induced me to buy my first Ford (a 2002) in 2006, which now has 102,000 miles on it with never a single problem. Of course, I'm a believer in regularly scheduled maintenance, and changing and checking fluids.
Obviously it's my opinion that Ford builds good vehicles, at least in my experience of them since 1997. I've also been very impressed with the three Fusions I've rented.