Hmmmmmmmmmmmmm...
First of all, I'm older than most of the others who've responded; say whatever you'd like, that matters.
The other thing is the kind of sex I require is not at all...um...vanilla. It takes a toll on both my partner(s) and me when it happens with all that intensity and fury on a daily basis.
That having been said, my libido swings in great arcs between hypersexuality and something approaching complete asexuality. My hyper cycles, which can last months, can approach the absurd, where once per day barely scratches the surface. During my low cycles (like the one I'm in currently), I don't even JO more than twice per week; that's an extreme low, but I've been there for at least the last few months.
The reasons for the lack of sex drive: low testosterone (my current medical care does not pay for TRT), unusually severe arthritis pain in my neck, a lack of suitable beaux (and an increasing pickyness as I get older), and I work a highly sexualized job in a highly sexualized environment, which jades me. I'm sure there are other reasons, but those came off the top of my head first.
I've also never been a morning person, and am less-inclined than ever to be one now. One of my most-beloved co-workers has this story of coming home from the bar we work at with a really beautiful guy, and evidently the sex was pretty amazing too. In the dreamy afterglow the guy asked my friend how he likes his eggs cooked in the morning. My co-worker's response was "alone!". The first time I heard him tell me that story, I knew we'd be thick as thieves.
One last thing: when I was just about to turn 25, I met an amazing man who was, in every way, my physical and temperamental ideal. We complemented each other perfectly, we were both young and each fell head-over-heels immediately. During our first six months, we had sex every night (sometimes more on days we were both free from work). After about six months of it, I found it to be much more of a chore than a pleasure. No other dynamic in our (admittedly stormy) relationship changed: just the sex, which gradually settled down to ~3-4 times per week. We ended up together for four years: in many ways, the happiest and most productive of my life, both emotionally and materialistically.