Did you miss that before Omega gave you the offer, you already had "the ability to emulate every possible universe of the complexity of the one we observe, and then some"?

To start with, suppose you have a 20% chance of dying in an hour, and an 80% chance of living for 10^10,000,000,000 years

By accepting Omega's offers, you're almost certainly giving up those 10^10,000,000,000 years of life, in exchange for some tiny probability of a longer but still finite lifespan.