In my last marriage, my (narcissistic-- aren't all exes? :) ) ex husband finally consented to counseling as a last-ditch quasi-effort. Needless to say, there was nothing he needed to fix, it was all my fault and a few months later, I moved out.
With my current husband, we'd been together as a couple for about 2.5 years and decided that since we were in a rough spot and both of us had failed marriages, counseling would be a priority. We did it every other week for about two years, and then once a month until we felt 'fine'. It was about 3.5 years total, maybe. Hard work? Yep. We found a very insightful fellow who was able to relate to both of us. His first step was to bring us back to the foundation of our relationship: what we loved about being together. He really built a bridge for us, and was willing to ask us-- and make us ask ourselves-- the hard questions. His goal, I believe, was not to 'save' us, but to guide us into habits which really improved our communication with each other.
I'll also say that, within our relationship, we've had moment where things have felt they've 'cooled off' a bit. Less passion, more obligations in life, sometimes just my internal angst... it's not all romance all the time. However, if we both feel like good partners to each other, and decide to make more of an effort with each other during those 'down' times, knowing full well that they're likely only temporary, that makes things better. Not getting "excited" about each other is not scary to me like it used to be... now I see it's just a moment in a long chain of moments with a person I deeply esteem and have a lot of admiration for. Change up the routines, get a baby sitter, even if it's only for a couple hours at a coffee shop or the pub or doing whatever you two enjoyed doing before you had children.
Counseling is exercise for the relationship. It can strengthen it and keep it strong.