The first few months of the relationship - that golden honeymoon period - are likely to be the times when you go out most. You take each other to restaurant, you see movies together, go bowling, weekend breaks and all that comes with it. You work hard to impress each other.
When you settle down and realize that you've both bought into each other, it's too easy to get lazy and let this go. Life becomes an endless cycle of work, home, sleep, repeat. The time you spend together should be a break from the boredom of everyday life - it should never become part of it! Make the time every month for a date or two. Go away for the weekend, travel, find a new favorite restaurant. Get out of the house and break up the routine. It'll keep things fresh and give both of you something to look forward to.