Shame, but what is the point if you can't pass on your experience. All the best to you and thank's for the help in the past! Will not have any trouble in sorting it!
There are plenty of people passing on their experience. You could also argue that there's no point if people don't listen to it.
The Omega petrol engines were indeed
originally specified with an 80K service interval for the cam belt and tensioners. GM were swamped with warranty repairs on the early engines where the tensioners failed to last this period by a wide margin and in response they issued a bulletin reducing the interval to 40k/4 years. Your dealer has simply not bothered to check this and is pulling a figure out of his head.
OK, so if you insist what your dealer says is gospel, that's fair enough. That aside, I would point out that we have significant independent experience with Omega petrol engines on this forum dating back many years. We have seen numerous cam belts fail where the 40k/4 years official service interval has not been adhered to and can categorically state that if yours lasts 80k you will have been very lucky. Most don't get much past the 40K interval. We have seen a not insignificant number that fail before even 40K.
Our experience is telling you that yours won't last 80k. A new belt and tensioner kit can be had for around £100 and it'll take an hour and a half to fit. Alternative is enough engine damage to write the car off. To paraphrase:
...you've got to ask yourself one question: Do I feel lucky? Well, do ya, punk?