I think this is largely a silly thread full of piffle, but I'll take a go at this, as someone who genuinely has sex quite a lot (I'd guess 10-12 times a week on average, sometimes three times in a day. We tend to have super intensive spurts when we're both feeling really horny (eg 8 times this Fri-Sun).... then pauses (eg once in last two days) to rest and reboot....
We both enjoy sex and have high drives, but yes there is a routine element in a few ways. There is a habit element- I guess most people's default in a long term relationship is 'no we won't have sex' then they need specific stimuli to turn that into a 'yes we will'. I feel we are the opposite of that. The default is more 'we will most likely have sex' morning and night, unless there is a reason not to (eg we are particularly tired or under time pressure). So it's a bit more like people who have a daily habit of going for a walk, kissing their partner good morning, or having a daily glass of cranberry juice.....whatever. You do it, because it's enjoyable and healthy, unless you are not in the mood - and we are normally in the mood! This default norm I feel is really healthy. It keeps us connected as a couple, it's the most regular exercise I get, it keeps me in touch with my own body, feeling desireable as the default, it freshens me up and just makes me feel I'm leading my full life, in touch with my physicality.
As it's a very very normal thing for us to do, there is definitely a feeling sometimes of repetitiveness. It's always connecting and enjoyable, and we are giving each other pleasure, and we also make a conscious effort to introduce new things, approach it freshly, just like everybody else does.... but there's no pressure that every single time needs to be eye-rollingly porn film kind of spontaneous and wild. Some times it's simply a calm, loving way to connect- equivalent to a long, romantic hug... other times it's more sexually focussed.
We do also have super charged sex, that breaks way beyond the routine if something has particularly stimulated us.... I'd say that's more about once or twice a week. Perhaps those are the times, when people who don't have the default to have sex, break through and do the deed!
I do think one's body trains itself,,, just like with exercise or healthy eating. The more you do it, the more switched on to that choice you become, and the more your body wants it......