I dont think running out and replacing the ecu when the second the car doesnt start is a good idea. The unit seldom fails, and one should do many many tests before replacing an ecu. There are plenty of problems that are not ecu related that could cause intermittent failures. If you crank and you dont have spark, you have to check the entire ignition system before replacing the ecu. And if you have spark, be sure if you have fuel...if you dont, diagnose that...dont just run out and waste your money on an ecu.
just my humble opinion.