We look back to find a suitable reference class and choose the believe in eternal life we are talking about other people and whether they made successful predictions.

It's also not possible to find compelling evidence that one doesn't have an eternal life in heaven when it doesn't come to pass.

All argument against the existence of an eternal life are as good the moment the prediction as made as they are later when the event happens or doesn't happen. Cryonics however makes claims that aren't transcendental and that can be evaluated by outside observers.