If you live in a California emissions/IM240 state, you cannot renew your registration if the check engine light is on.Why do you care if the 'check engine' light is on?
Bought my wife's 99 Taurus wagon used about 15 years ago. The 'check engine' light has been on almost the entire time - I could care less. The car runs fine, delivers the rated fuel economy, I keep the oil clean. Not for nothing do mechanics call it the 'money light'. The fact that your mechanic was just blindly throwing parts (and your money) at the problem shows that he/shed doesn't know what the problem is.
Only repairs I've had to do over the years: fuel pump, belt, crank sensor, water temp sensor, and a junk Fram oil filter with a pin-hole leak.
My car, 02 Chevy Cavalier, bought used for daughter, now I drive it, 'Service' light's been on the entire time -- doesn't bother me in the least. Car runs fine, good mileage, I keep the oil clean.....