Consent, desire and needs: the dilemma

*SSC is sacred. It is a paramount cornerstone of trust. I would not question the practices of informed consent. This post is not about questioning consent. I want that clear from the start.*

I have been considering a Facebook group post. A woman's husband came home drunk and declared it was her "wifely duty" to fuck him when ever he requested. Oh corse this erupted into a deluge of angry responses. The husband was a misogynist, it was rape, what an asshole... and for the most part I agree. A persons body is their own to do with as they please. Consent is after all given and revokable at any time.
As I considered the issue brought up by the post. Specifically, I though on how interest and desire seem to wane in long term relationships and how consent is tied to desire. If only one has a desire than the other is either doing (knitting , fucking, antiquating, bottoming, what ever) things either out of pity, to please the other or just to get along..... is that really consent?  I begin to doubt it.
Since consent involves desire or will to do something then if or when that will changes the consent changes. It is natural ... I get it.
In my past I have had Vanilla relationships go bad because after the desire was met my partners religious guilt welled up and suddenly the consent so freely given ... her desire to shove me down and ride me like a show pony... was reversed. Suddenly consent was now conjolled out of her and she "was talked into"  it.  As soon as the desire returned she was a willing horn dog again. This relationship has left me with a sense of impermanence to consent, a "retroactive revocability" if you will.
This is the terrifying territory of the "treacherous submissive". The dangerous one that begs for play but then latter claims violated boundaries or tell some sorted tale. Their consent abates with their desire.
The harder part is when the desire abates slowly. They become "less interested in BDSM or sex (remember I am speaking of all partnerships here not just Fetish ones) and more interested in tv, movies, computers, books .... distractions.
Many will say "I'm too Domtastic for that to happen to me"  Trust me at some point a submissive has been tired of your Dom-Ass. You were either too arrogant or too busy looking for the next thing to notice.  In the Lifestyle I have been through this on more than one occasion. it is natural for a relationship to go from roaring fire to warm hearth. The problem lies when that warmth holds comfort but no real desire.
So when the partner that was hot to play becomes the trusted friend , companion, lover that is comfy and no longer desires the same as the their mate / Top... where dose consent lie then?  When the slightest hint of play brings on a yawn or , in the case of my ex a disapproving look over the top of her latest book, how can a good partner expect there to be real consent?
Remember you have needs you want fulfilled. Needs that have brought you to this person but with out mutual desire those needs become a burr in the saddle. If you aren't familiar with how bad that sucks ... ask a pony girl.

So here is the delema:  How is the good partner to act in the face of flagging desire and consent considering their own needs. To demand, conjole, "negotiate", bater or force what one partner needs over the other is ,IMO, a violation of Consent. How should that drunken bastard really been? How do we meet our needs AND our partners in this kind of situation.
The Nilla hetro way is porn, divorce , cheating..... or religious self loathing. Many in the lifestyle, myself included, are in "open" or "Polly"  relationships.   But to us in the lifestyle with the Top being somewhat expected to drive the activity.... how do we balance the consent of less desires with our own needs?  Sure 24/7 and TPE are less likely to be affected by this as openly as those not practicing D/s in that way. To be sure though there are days when either party is "just not up for it" and then it is not as much consent as commitments to meet.
There in lays the issue. While the desire to see their partner happy may replace their desire to play, serve of have sex with their partner it is a *duty bound* thing , a placation at best. I do not know about you but I have worked too hard at honing my skills as a lover, Dominant, and many other valuable things to be a "house hold chore".
In the end there is only one cure when faced with this issue: Honest, clear, communication.  Not just between partners but also within. What is the reason behind the decreased desire?  What are the permitters to getting needs met? How important are the needs that are not getting met? Is it in the end a deal breaker?  Communicate honestly with yourself and find answers to share with your partner.... Then see where things stand.  In the end Desire and the consent it brings ... can not be forced only understood and dealt with.