Suppose there is no afterlife, and God offers you a deal. He'll put you in a coma for a year, but give you two extra years of conscious life to compensate. Pretty good deal, you go for it. Moreover, God surely has the right to do the year of coma plus two years of conscious life thing even without asking you. We have no rights of autonomy before God. He may need a good reason to do it, but it does not have to be a very serious reason. Your family's learning to appreciate you a little might easily suffice.
Elevate this to a principle:
- God does not need a very serious reason to make you unconscious for a year when he gives you two years of conscious life to compensate.
Here's another way of putting the point. If you are going to have an infinite conscious future, your infinite conscious future is no less for your sleeping through a year. Granted, that exact year that you slept through has been missed. But the subsequent years are different for your having slept, and you wouldn't have had those years had you not slept through that one.
Now, one might think: Therefore we have the right to make others unconscious without a very serious reason, if we think everybody has eternal life. But that does not follow. First, we can have rights of autonomy against each other that are not rights against God. Second, by making a person unconscious for a year, we typically do decrease the amount of her conscious earthly life. Of course, so does God if he makes a person be unconscious for a year. But what is most problematic in decreasing the amount of someone's conscious earthly is that it decreases the time available for the tasks that God calls the person to. But God can easily take all that into account (e.g., by increasing the intensity of grace during the other years).
If this is right, it makes it much easier to generate a theodicy for comas. But I think the same reasoning may apply to anything that is less bad than being unconscious for life. For instance, it is clearly better to be conscious but mentally challenged than to be unconscious for life. And many pains are better than being unconscious for life.