So I'm coming along in my skills.
I noticed something. I was talking with separate girls after classes just outside the library on my campus. I can be talking with them, getting IOIs, they contribute to the conversation (the shyer ones I have to banter and share more before they do, which is OK). I will eventually say 'nice talking to you' and go about my business. The next day, or next week I will see them again and talk and not get near the positive response.
I am familiar with the concept of buying temperature.
Is there an "ask out/get my number window" for women? Like if I miss the window and leave it won't be back.
One girl went cold, the others are still friendly but not near as interested.