I've watched people around me go through this exact thing and honestly most of them were panicking over nothing. The first few years are basically your brain on overdrive - dopamine, novelty, all that stuff. Five years in, yeah, that chemical rush settles down. That's not a problem, that's just how human brains work. The couples who made it past this phase were the ones who stopped waiting for butterflies to come back and started actually *building* something instead.
The trap I see people fall into though is confusing "the spark is different now" with "the spark is gone." Those are completely different situations. If you still genuinely like each other and want to be together, you've got something solid. What kills relationships isn't the fading of early-stage intensity - it's people getting bored *with the relationship work itself*. Like, you stop talking about real stuff. You stop trying. You stop doing things together that aren't just... existing in the same space. Routine isn't the enemy; *stagnation* is.
Real talk: the question isn't whether butterflies should still be there. It's whether you two still actually *engage* with each other. Are you curious about each other? Do you make each other laugh? Can you talk about something that matters? If yes to those, the "spark" you're missing is probably just the adrenaline, and that's fine. If you're realizing you don't actually know what's going on in their head anymore, *that's* when something needs to shift.