I think my morality is kicking in because I suggest things like I could potentially help with bills or whatever as we progressed together but know that likely will never happen.  

She is not planning to hit it and quit it?  
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I have never met a POT SB that was looking for a one and done, but I've seen plenty of BCD action that ended as a once only experience.  
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Did it she plan it that way? Was I just too fat and ugly to fuck again? Did she meet a guy with a much bigger wallet? Was she just trying to get enough cash for a one-time need? Did I have halitosis? Is she allergic to my cat (yes, this happened - she almost went into anaphylactic shock in my bed room!)? Is the drive too far? Did she get arrested? Did she get beat up by her pimp...er... boyfriend? Did she get a raise at work (by screwing her boss)? Did she win the lottery?  
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Speculation can be endless. But in the end... Who cares?  You got laid. Be happy.  
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Yet another reason why you NEVER pay in advance! Imagine if you gave her $1000 for 4 visits that month and she bailed after the 1st BCD. Yikes!

these girls have enough...what did that chick from the earlier thread say, oh yes: "assholes and douchebags" screwing with them, we don't need to be another. If she has a tag for "Short Term" then OK, otherwise play nice.

After the M&G, if I don’t find her physically attractive, I won’t even say things like, “Let’s get together again.” I will definitely not mention any arrangement or things of that nature. Conversely, if she doesn’t ask me to text her again, I just assume she is not interested. Sometimes, that is not even true. Some are not interested but just want to be polite. Anyway, I don’t want to lead people on just because I was horny that day. It is much easier with hookers; you fuck her once and disappear, no guilty feelings at all.

especially during relatively dry spells when I just didn't have any truly interesting prospects.  So I lowered my standards and dated a few who were ok, but not repeat worthy. I dated 3 in a row like that once, and they were all fun one time dates, but all 3 were heavier than I expected, so no real chemistry in the bedroom.  But I feel ok about it since I never promised them any more than that.

Without a second thought.  When they hide their true weight and are just huge, yes.  I’ve  fucked them and forgotten them.  

I ALWAYS hope to make a lasting connection when I fuck her the first time...and I NEVER take a Fuggly lady BCD just to get laid !
But around 50% of first fuck dates for me with SB's are one time shots...I'm just very particular about making a great connection and if the sex or her attitude is not up to par I move on quickly to find better action.

Ive had probably 6 or 7 GREAT fucks and a whole lot of "im hlad thats over".......especially with the too young  and milfs

I try to make sure that we have a connection  before meeting so it’s more of a formality and we go right into BCD  

 I meant one recently and we hung out that evening and she was completely obnoxious. I’ll she did was talk about herself until all kinds of lies about how great she was in previous lives.  She was pretty damn nice to look at so we ended up spending the first night together but by the time we got back to my place I knew I did not want to have to put up with her lies and self-centeredness

From what I can tell by rereading the OP's post, the original question is about projecting a desire for an ongoing arrangement while "knowing" it will be a one-off bang and run. Yet the discussion above seems to have morphed into a more specific scenario of banging a marginally attractive SB for an HIQI (Hit It and Quit IT) but telling her you want a LTR, presumably to get her to close the deal.
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My response was based on the broader question without the "marginal attractiveness" component. My point was that any 1st time BCD can be a one-off. There are not assurances of an ongoing arrangement at any time.  
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If I consider the additional context of attractiveness, then I follow the GaGa doctrine; if she's not hot enough to fuck multiple times, she's not attractive enough to fuck once. I have way too many options to need to give a SB a mercy fuck just so I can get off.  
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On my worst days of unsuccessfully trying to schedule one of my SB's or local Pro's (including local Porn Star escorts), I can still go to any of 4 strip clubs within a 12-mile radius of me and get a decent BBJ/HJ, sometimes FS, and sometimes even take home for $200-$400.

Takes too much effort to recruit, meet/greet, and get BCD for one and done.  So I never plan it, but it has happened.  One SB was phenomenal in bed, but just talked too much.  Way too much!  Couldn't imagine going back for more.  Another SB was a closet smoker and had saggy skin from losing a bunch of weight.  Shut down our 1st BCD event after 1 shot.  Repulsive.

I’ve met SBs before and been pretty attracted to them, to the point where I know I won’t even need viagra to bone them, but after the novelty factor wears off and I see there are maybe hotter SBs on SA or pros on Hx, I stop seeing them.  So more and more I try to stick to only ridiculously hot SBs, even if it means cutting through serious GPS.