Leonard Nimoy, who passed away in 2015, had never expected to return to the Spock character. He thought, after the Star Trek VI: The Undiscovered Country, he'd donned the Vulcan ears for the last time. Then J.J. Abrams, Alex Kurtzman, and Robert Orci presented him with a story idea that he found he couldn't say no to. And that was the part of Spock Prime. Back in 2008, in an interview with Star Trek Magazine, Nimoy said he "had a grand time" reprising his character.
"“I found myself thoroughly enjoying it. I was very comfortable, and I don’t know how to account for it. I felt like a grandfather with a bunch of intelligent, evolving grandchildren, watching them at work, and enjoying working with them. I just felt very good about it – I felt totally at home doing it.”"- Leonard Nimoy
Beyond enjoying himself, Nimoy says he found " a certain peace" in playing this version of the character.
"I think I found a certain peace with the character. The character I play as Spock in this movie is a character who is at peace with himself, whereas the Spock that Zachary Quinto has to play is in a condition that is prior to what we saw in the original series, and not quite as evolved as he was in the original series. He’s in the process of finding himself. He’s putting together the building blocks of his character that will arrive at the character that I portrayed in the original series. During the course of this particular movie, he finds a peace as Spock, and grows into the Spock that I portrayed in the original series.”"- Leonard NImoy
The Spock Nimoy played on Star Trek: The Original Series seemed to be at peace with himself as well. He has some trials, but, overall, that Spock had accepted himself for who he was, but it's understandable that so many years later, Nimoy would find even more peace with the character.
And while Zachary Quinto may return as Spock in Star Trek 4, if the movie ever gets completed, for now, Ethan Peck has taken on the role, playing an even newer version of Spock. Both actors have embraced the character and taken it on as their own. Their versions of Spock have been imbued with subtle nuances that make him stand out in those particular versions. Coming after Leonard Nimoy had to be quite a challenge for both actors because they know as much as all the fans do that Nimoy was and always will be Spock. And it's heartening to know that putting on the Vulcan ears again was such an enjoyable experience for Nimoy who will always be missed.