Companionship is by far the more important, one might argue. Passion is fleeting, or can take place without the aid of a single emotion other than a desire for each other. It might last a night or continue for months, but the only time attention is paid in any great effort is while the passion is taking place. By contrast, people who offer companionship put into the relationship their effort, concern and time. It goes deep between the two, lasting beyond hardship or cooled passion or the ordinariness of life. Companionship/passion has been written about throughout the ages. Passion ignites and is volatile verses the lasting stability of a true companion. Most cultures see them both as important but play different roles at different points in a lifetime.
Because they are very different in function many cultures separate the distinct types of love-companionship (also known as comfort love) and romantic love (where lies the passion), or try to balance the forces of both, while others claim they do not need to take place with just one partner nor are they equally valued or honored.
Comfort love is a deep affection for those with whom our lives are shared. It involves such feelings as friendship, understanding, compassion and a genuine concern where another’s welfare comes into play. In comparison, companionship sounds easy but is by far the more demanding of the two (outside of the demands of a physical relationship).
Romantic love is more selfish in its time with a partner, and always demands that partner, while companionship means making the most of the time two people have, for not just being together, but togetherness. It is the moments that two people occupy particular slices of time and those times are fulfilling, enjoyable, and, often, do not involve sex.
Companionship is not all consuming as the passionate/sexual relationship. It allows that two people are individuals, have other interests outside of themselves, and are in no way bound by or to the thoughts and beliefs of the other. It encourages individuality and freedom of choice; more of an equality issue out of mutual agreement and respect. It may very well be more of a spiritual connection, where as things such as laughter, comfort with one another, and the sharing of intimate feeling are expressed as opposed to explosive energy.
As time changes, and people, with their passion and/or sexual desires fading somewhat, it is good to know that good companionship, as it has done throughout the relationship, will be what remains true for the rest of the partnership.
All relationships need a feeling of 'right' and the constant of companionship is what ensures the success of the relationship. It is being committed, even when the task is not an easy one. It is the sugar in the tea; the chocolate and nuts on top of the ice cream.