“The Big Bang Theory” has consistently bucked trends, including the one that would suggest a comedy in its eighth season might begin to grow tired and stale. Instead, the show has kept clicking on all cylinders, moving the characters forward while continuing to revel in scientific jargon and sly pop-culture savvy. That said, there’s a reason why the writers have kept the various romantic relationships from advancing too rapidly – presumably some of them watched “Friends” – which perhaps explains why the season finale (and SPOILER ALERT if you haven’t watched) essentially just kicked more than one can down the road.

The episode opened with Sheldon (Jim Parsons) and his long-suffering girlfriend Amy (Mayim Bialik) grappling with their very different ideas about commitment: She wants to talk about what it means that they’ve been “together,” such as it is, for five years, while he wants to talk about whether it’s worth investing his time in watching the CW’s new “The Flash.” (Frankly, it’s a surprise he’s not already on board that runaway train, if only in the service of Warner Bros.-sanctioned synergy, but never mind.)

Meanwhile, the Sheldon-Amy debacle triggers a discussion between Leonard (Johnny Galecki) and Penny (Kaley Cuoco-Sweeting) about their long-dormant engagement – the two actually agreed to get married at the end of last season – leading to a spur-of-the-moment drive toward Las Vegas, an awkward confession and a not entirely satisfying cliffhanger.

As if that weren’t enough, and as a tribute to the show’s depth now with its expanded cast, there were two more interrelated plots in the script credited to Steven Molaro, Steve Holland and Eric Kaplan. Howard (Simon Helberg) and his wife Bernadette (Melissa Rauch) wanted to evict houseguest Stuart (Kevin Sussman), while Raj (Kunal Nayyar) has grown increasingly uncomfortable with his more adventuresome girlfriend (Laura Spencer). Both the couple and their pal, as it turned out, were too sensitive to deliver bad news, meaning those problems, too, will fester into next season.

The final scene, in which Sheldon revealed his plans to propose to Amy right after she had asked for an understandable break, was clearly an “Aww” moment, sure to be embraced by fans caught up in that wondrously odd relationship. But it also felt a tad unconvincing. Yes, Sheldon has professed his love for Amy, but it still seems almost impossible that he could accommodate another person completely in his self-absorbed approach to life, which has been so well (and hilariously) established.

Still, “The Big Bang Theory” has become particularly adept at weaving together poignant moments with big, broad comedy. That included the sendoff earlier this season to Howard’s mother, incorporating the death of the actress who provided her voice, Carol Ann Susi, into the program.

The writers have already exhibited considerable guts in moving Chuck Lorre and Bill Prady’s creation quite far from its initial foundation of four socially challenged geeks and one beautiful neighbor. Yet having already married off Howard, there’s probably some wisdom in not hurrying to fundamentally change the living arrangement between Sheldon and Leonard, with at least two more seasons of the show already ordered.

Indeed, the other unspoken question besides “Will you marry me?” is how long CBS can keep the fabulously compensated cast together. As it stands, the clock is ticking on the network’s struggle to develop another hit that can take the baton and run with it, in the way “Big Bang” did from Lorre’s recently departed “Two and a Half Men,” after the latter got its start behind “Everybody Loves Raymond.”

Of course, as valuable as the show is – not just to CBS but also to Warner Bros., which produces and syndicates it – there’s plenty of incentive to keep “The Big Bang Theory” from burning out anytime soon. So while the guys keep grappling with the imponderable mysteries of love, marriage and a commitment that goes beyond the run of a superhero drama, with those factors complicating the equation, don’t throw bouquets at them just yet.