RE: How important is sex in a relationship?
I think it is very important. But as Esther Perel says (I recommend everyone to read her work) this is the paradox: the more intimate we get to be with our partners the more our sexual drive towards them gets lower. Very often we lose our individuality because we get so into making the relationship work. There is no more "I", there is only "we". We think that this helps a relationship but it is exactly the opposite. I think we each have to have our own thing: travel alone sometimes, go out with our friends without our partners, have a hobby or a passion that doesn't include the other, etc. And also very important: don't demand things, don't impose anything. Love is freedom. Here's one of my favorite videos on this topic: https://www.ted.com/talks/esther_perel_the_secret_to_desire_in_a_long_term_relationship