Just best friends living together

One of my friends confessed that she and her husband have become "just best friends living together". They joke about it, but they know it's true.
They're been married for two years now.

She often sleeps over at her other girlfriends' house and spends a few nights at their home. They havent had sex or kissed in a year because "you don't kiss your best friend".

They were a couple for 10 years before getting married and since then have bought have a huge house, 5 cars and properties in their name. She says its easier because they get to keep all the possessions, they enjoy their time apart, and have an unspoken understanding that that is what they've become.

I asked (me being the single friend) how that will work out in the long run. She said they're just going with the flow because it's easy. She's not involved with another guy or anything like that. He might be, but she's not sure (and I dont' think she'd really care).

I'm amused that they chose that arrangement, but as she said, it's easier. I gues I just want to hear the opinion of married people on the matter.