Lois Lane is the only absolute need for Superman. I'm okay with her not appearing all the time, not in every adaptation or elseworld. Superman still needs to be a character that can function on his own. But Lois needs to be there, at least in spirit. Onto the Kents.
We know they can function alive or dead. They aren't an absolute necessity in Superman, but they are welcome. The people who like the Kents (or one) around in Clark's adult life usually do so because of outside adaptations, as you can see in many comments here. The anti-New52 crowd points and go: "See! See! This is why he need the Kents!". Lastly, you have comic book readers who grew up with post-crisis Superman. There are pros and cons to all arguments about the Kents presence in Clark's adult life.
As for me, I'm—sorta—the adaptation crowd. I didn't get into comics until about four or five years ago, JL/U was my entry point. I did re-watch the most of STAS when it was on DCUni. However, I'm very pro-creator when it comes to these characters. So, Jerry Siegel and Joe Shuster had the Kents dead, then they should be dead. The Kents are only needed to raise up Clark.
So, should they be around in Clark's adult life, does it matter? Superman is still Superman with or without them. You can write stories with them dead, never being in his life, or anything else. Prior to 1939 and Superboy, Clark was an orphan who decided to us his strength to benefit mankind on his own, he didn't need the kents.