Its relative to how quickly she normally sleeps with guys.
I want to be in the group of guys she was most excited to sleep with. So if I know/suspect that she's had sex right away with other guys but wants to take things slow with me then Id feel like she doesn't desire me as much and Id lose interest.
Just to be clear, I am not saying I would pressure her, Id just end it. She either desires me or she doesn't. If she doesn't Im not going to try and force her to feel something she doesn't but Im also not going to stick around.
Now if I believe she's the type of girl who is always hard to get, and always takes things slow then I have no issues with that.
Obviously I'd want it as soon as possible, that'll show me that she's serious about me and not using me, but I don't expect that. I think after the 5th date, if there's no sex, then something wrong is going on.