If taken care of properly, the 1.8 has an amazing amount of life in it. I had my first mechanical at 244,000 miles, a broken exhaust valve spring, and decided to go through it completely. The crank and cams still measured into factory specs and although the first compression ring showed some blow-by, the second compression ring did not.
One of the reasons for the longevity can be attributed to the fact that it was designed to be turbocharged, so it is somewhat overbuilt for the stock 127 horses. Acura Type R knuckleheads bragged about their oil cooling jets under the pistons, while our 1.8 has had them since 1990, or so, when Mazda first began using it. We also have some semblance of an oil cooler. Most folks have never noticed it, since it only appears to be a base for the oil filter.
Do your homework on the history of the particular car, oil changes, repairs, what kind of guy you feel the owner to be, etc., and it will help you make the decision. It would be adviseable to have a mechanic take a look and run a compression test on a car with a number of miles, as well. You can never be 100% sure, but you can eliminate some of the variables in buying a car, if you are willing to put in the effort.
Oh, yeah, I have 269,000 miles on the car, now, and am completely jazzed about my rebuild. For comparison, I am running dead nuts even with two of my buddy´s cars, an Audi S4 and a Honda S2000. Not bad for the Rodney Daingerfield of cars..."It don´t get no respect."
Marcus