Sorry, the male perspective (or at least half of it) has been making a bacon sandwich and watching TV.
Most people have heard about the '3rd date' thing about sleeping together. That's a general expectation, so if, for example, you invite someone back to yours for a home cooked meal, then they'll be justified in thinking sex is on the agenda.
But it's down to the individual, completely. Personally I think the longer people wait before DTD, the stronger the chance is that the relationship might bloom. There are lots of anecdotal stories which disagree with that, and I don't know of any large-scale laboratory controlled research projects which bear it out.
Speaking from my experience though, I've had long term things come out of relationships where we've waited for 2 years (when we were teenagers), or 5 or 6 weeks (students) or a month or so when older.
There have also been a couple of relatively medium term things - a few months or so - where we DTD on the 3rd or 4th date. Mostly though I go off someone after sleeping with them the first time unless the emotional connection is there already, in which case I fall massively in love with them. So I choose to not do second dates with someone if I'm not feeling a strong connection or spark with them after a few hours of conversation, so I don't end up DTD with them and dumping them afterwards.
Sex doesn't have to be an emotional, lovey, romantic type of thing. It can just be physical fun between people who enjoy it. But if you have that kind of sex, it's unlikely, in my opinion, to turn into the other kind.
just my opinion of course.