Nothing is more important in an intimate relationship than sex and keeping sex spicy is the key to longevity.
The foreplay that we all use to draw our partners to us sexually in the beginning of any intimate relationship will wane with time. It's only natural for the excitement that you felt early on to morph into something else. That doesn't mean sex can't still be fresh and exciting, but it does take thought, effort and sometime creativity. Think of it as we do food, hey they kind of go hand in hand. Both food and sex are two things in life we can't live without and often crave. So it's nice to add a bit of spice to both these joys in life. How you choose to spice up your sex life is entirely a personal unique decision that only you can make.
I think one the key components in having a great sex life to begin with is communication. You must first know what makes your partner happy in the bedroom and then have the desire to please him or her. That sometimes takes creativity to maybe surprise your lover with a spontaneous lunch meeting that leads to making love in a beautiful romantic setting, such as a picnic.
Perhaps you are the type that loves to dress up in lingerie and role play? Maybe you want to whisk your lover away for a sexy weekend in a remote local? Whatever it is, thought and creativity is sometimes required to spice up a long term relationship. This should be fun and desirable for both of you. I personally love planning trips, getaways and spa weekends to relax and unwind with my man.
Initiating sex at home with a romantic setting and a great meal can also be fun. Sometimes just staying in bed all day making love and ordering in Chinese is spicy enough.