Extending The Shelf Life To A Longer Lasting Marriage

In the beginning, marriage is so fresh and new. I wonder if we worked more on keeping that marriage alive, instead of worrying about the nuptials (all the glitz and glory of getting married) would help make things work a little longer. If we paid a little more attention to our spouse at the end of the work day, instead of letting them just go, would we be able to stretch our marriage to a longer shelf life?
When we first get married, we really do spend alot more time working on things with our partners, but as time progresses, we tend to get very busy in bills, work, children, and basically, life in general. Where did the time go that we spent with each other? As things get into a routine, are you happy? Is your spouse happy and how do you know? I think that mostly, we know if they are happy by paying attention to what is going on with you both. Do you go out once a week and enjoy alone time together? Do you still have conversation? I think both of those things are important, as well as keeping up with each other's "outside the marriage" life.
How can we keep a marriage happy and longer lasting? Got any other ideas? I'd love to hear them if you do.