Keep the sex in your marriage fun. Always keep a good balance of predictability and mystery. Thus the phrase planned spontaneity. Just because you may have to plan sex does not mean it has to be routine. Planning the time means it is important enough to make it happen. Many couples I see have no idea how they got to the point of having sex five times per year.
Some ideas:
Meet as “strangers” at a hotel bar. Have a conversation and “get to know” each other. And leave with the “stranger” you meet to go to your room (that you already had) and have great sex.
Have sex all over your house. Take away the routine of only having sex in only the bedroom. If you have kids get a sitter or trade off with a friend so you can have time alone.
Do some foreplay with each other, be romantic. Build up to the experience don’t have the same routine.
What do you think, did I miss anything? I would love to hear your comments, questions or thoughts.