I keep at least 6-8 girls (usually more) in my rotation.
So if one of them starts to fall flat, I don't care.
But I flirt right from the start. So I set the tone immediately as being fun & playful. If they respond, I've already established that frame.
If they're not into it, I know right away & I don't spin my wheels on something that's gonna fizzle out after a lot of effort.
Although, sometimes I keep those "tough ones" in rotation, just to experiment with. I'll let 'em go cold & then after a couple weeks, re-initiate with a silly message just to see what happens.
(Sometimes that 2nd round sparks a fire)