There are some forms of affection that I feel are acceptable in public, such as holding hands or embracing, or even kissing. But it should be done in a such away that wouldn't grieve the Holy Spirit. One should not be ashamed or embarrassed by you spouse attention in public. Let love be your guide and cherish every moment for you never know when it might end, and then you have to deal with the regrets, because of false pride.
If passion and desires are not in a marriage, then something is vary wrong. For some reason or reasons the fire in a marriage seem to die down with age and I don't believe that should be the case. They're part of God's design whether your marriage or not and the normal function of the human body. (Some have chosen to sacrifice those desires in order to be one with Christ in celibacy.) However, to refuse your spouse these pleasures and rights is wrong and reveals there serious problems of resentment and unforgiveness. (Sometimes that's why other people have affairs or get into pornography, but it's not the unpardonable sin. They should be forgiven as soon as possible, because God has. It's also good for ones own health. There are consequences for unforgiveness. Your spouse is not a possession, they belong to God and the Body of Christ, and jealousy is not acceptable. If they are give true freedom, they will rarely want to leave you.) Whatever the problem is, it needs to be taken to God in prayer so He can restore the heart issues. Neither should one use these pleasure to control, manipulate or punish their spouse in order to get their way.
Note: Here's what the apostle Paul wrote the church of Corinth, regarding the subject of sex, and he was a single man of God.
"The husband must fulfill [render] his duty to his wife, and likewise also the wife to her husband. The wife does not have authority over her own body, but the husband does; and likewise also the husband does not have authority over his own body, but the wife does. Stop depriving one another, except by mutual agreement for a time, so that you my devote yourself to prayer, and come together again so that satan will not temp you because of your lack of control." (I Corinthians. 7:3-5)
I have never heard a minister preach or teach on this subject. I wonder why? However, I do know that some have, but not enough of them. Also it seem that Christians who do not have an intimate relationship with Jesus Christ will rarely have one with their spouse. Marriage it about forgiveness and intimacy is a good way of showing it. Most people live their lives far below what God had intended them. I'm believing that will change in this next move of God.