Have you considered for even one moment that immortality would be a sentence of eternal Hell?
Any mind that is not itself infinite would, at some point, experience everything it can. This point would by definition be before the end of eternity. Even if said mind was somehow ever-magnified and expanded, it could only asymptotically approach infinity.
At some point further out (yet, you note, not actually any closer to infinity than the previous) you'd still hit a limit. This is for all experiences, meaning all permutations of all themes you can think of and all those you can't. Still no closer to infinity than before. Boredom becomes infinite. You've seen and done it all, including eventually taking pleasure in the kind of torture that would scare a Hellraiser Cenobite, and for basically the same reasons as them.
Don't even try that "heaven is infinite blissful experiences" crap; no such thing as infinitely different experiences for any finite mind, however large, blissful or otherwise. And if experiences begin to repeat, the effect is essentially reincarnation, an admission that eternal continuity of consciousness isn't that great after all. And then you're like a skipping gramophone record, eternally running in circles. Some reward.
This is another reason I just sigh and shake my head when hearing Muslims or Christians talk about paradise; their imaginations are so completely stunted and limited that the above never even occurs to them. Even the ones who figure out that spending eternity kissing Yahweh's ass is a raw deal wander off into some nebulous "I don't know what'll happen but I'm sure it'll be okay" tangent rather than think critically about these things.
This is why our end goal has to be annihilation of the ego, but in a positive sense rather than a negative one. This is why the end goal is to sublimate back into "Source" or "God," whatever you wish to call the ground of it all. Do you see now?
It seems that the ego plays a big part in what we think of an afterlife. I was raised Catholic and I was told that heaven is going to be like it is here on earth. The little home with all your friends gathered at the table cracking jokes. I was at a funeral a few months ago and the dead guys best friend was saying "he's up in heaven now talking to everyone because he loved to speak to strangers." I'm thinking no he's not. He's dead. Hey, if it helps him cope with the passing of his dear friend then I can understand. I just think it's silly that many people are conditioned to believe that heaven works like that.
It's one of the reasons why I gravitated to Buddhism in the last few years. It's not really a religion though. But, I do treat it as such. And, if you've ever been to SE Asia you'd see that most people there treat Buddhism as a religion.
The Four Noble Truths:
1) Life is suffering.
-In the West, we are taught to ignore suffering. That it's not something that we should talk about, but the truth is there is suffering in our world. To ignore it is at our own expense.
2) The truth of the cause of suffering.
-Instead of looking inward, many of us are looking outward to find meaning. But, this never satisfies us. Many are left frustrated that the world isn't bending to our demands. This is also where attachment to our way of thinking. We become slaves to our mind. To materalism.
3) The truth of the end of suffering.
-Detachment is key here, because attachment is the root of suffering. So, how do we end suffering? By detaching and looking inward. This is why I love love love mediation. It forces me to look inward which is a very difficult thing to do.
4) The truth of the path that frees us from suffering
-You could call it being enlightened or awaken. It's the path that most people never find. Most people go thru life ignorant. It's not just Western culture but the world. They go thru life in a derp state. Never awakened to what's possible.
Many people who say they are Christain or Muslim are stuck in the suffering phase. Attached to their religion. That everyone else be damned. Well there are 4200 religions practiced worldwide today. Before the Europeans inhabited America and slaughtered the native population they had their own religion. It wasn't Christanity.