SB's may leave you for a lot of reasons, most typically around a bigger wallet. We've had ample discussion around why they bail. But we rarely talk about what makes an SB stay.
First, as netnoy advised, make damn sure she gets off first and often. Shouldn't be a problem for you, but in case it's not obvious, get down there and relish every moment of that fresh, tight pussy. Most guys her age will typically try to go for the BJ then penetration in hopes of getting off before she changes her mind (i.e.: sobers up). At best some guys will spend just enough time for them to check the pussy eating box and then move on. So indulge your appetites and work hard enough to keep her happy. When she starts to scream and pull your hair, you are heading in the right direction
Next, listen better than you talk. We never stop learning, no matter how old we are. Take a genuine interest in her interests, experiences, culture, etc., and ask her questions. Learn from her. She will indirectly notice it and it will help reinforce her self-esteem when she is with you. Again, most guys her age are generally expressing full-blown misogyny and will try assert some bullshit alpha-male dominance. You want her heading home after a date thinking you are a really good guy who understands her without being a simp. Just remember that being nice does not equal being weak. Always be nice, but never be weak.
Next, take mental notes on what she talks about, then do some research later. Google is your friend. She won't expect you to be up-to-speed on the latest Rave trends, but she will be impressed when you make a comment or observation about something she mentioned during a past meeting.
Finally, admit when you are a (cultural) fish out of water. Lying will just make you look fake. So be authentic and use that admission to ask her questions about what interests her and why.
As I implied at the top, SB's start an arrangement for the money. (I've never met a POT who was only trying to fuck guys over 60, or 70, or...) SB's stay in an arrangement when doing so makes them feel valued, appreciated, capable and empowered. SB's leave when they get bored, feel like a whore (unless she's into that), and of course when a significantly better financial opportunity comes around. But if they are happy with you, they are much less likely to LOOK for a significantly better financial opportunity.
Life is good
The Cat