Will Becoming friends with benefits ruin the friendship?..

Eventually it will.

You can only be friends with benefits for only a short while until things start to go horribly wrong.

First someone starts to catch feelings and begins to expect more.

Emotions are heighten at every single display of affection, displays that normally would have been waved aside.

There's just no way Friendship with the intent to benefit won't ruin a cordial relationship.