This is a great question. I'd like to say that, no, his opinion doesn't change. That would have made a better end to the story, I think. But the story ends with the lawyer writing a long note about his time in prison and why he is forfeiting the bet five hours early. Early in the note, the lawyer writes this line:
With a clear conscience I tell you, as before God, who beholds me, that I despise freedom and life and health, and all that in your books is called the good things of the world.
The lawyer writes that he despises life. To me, that seems like a complete turnaround from his earlier statement at the beginning of the story. That was when he argued that any life was better than no life at all.
Of course it is odd that the lawyer walked away from the bet to presumably keep on living. I'd be curious to see what his reaction would have been if someone offered to kill him. Or I'd be very curious to ask him if he would rather have been killed fifteen years earlier. From his letter, it almost sounds like he wishes for death, but he would not have that attitude if he wasn't allowed to live, read, and research for all of those years.