What are the good ways to liven up a marriage?

We're in our 40s. We've been married for 17 years now and things are humming along. We've been respectful and responsible in our actions towards each other, and we love, accept and support each other. Of course, we also squabble, but the bottomline is that we are comitted to each other. We also love our kids (9 and 11) to the bone. I wouldn't trade my life for anything else. The question then is, is this all? Where have the spark, the romance, the flush of emotions gone to? Is this it? Would love to hear from people out there.