It’s Been a Long Time

Like any popular coinage, the more it's used, the more people will associate it with one thing.

Same with Netflix and chill.

Since the rock and roll?

For my age group, “It’s been a long time “ = so don’t rush me.

What makes you think it is? It's what someone might say at a restaurant when the server brings out the meal you ordered an hour ago. Or someone asks when you last bought a new car. Or when you're waiting for your chess opponent to decide on his next move. I don't think there's anything to your premise. As far as your example goes, it's sort of natural for people on a date to give a sexual inflection to rather neutral statements. It can actually get tiresome.

Ooh Yeah.
Been a long been a long lonely lonely lonely lonely time.

It's Been a Long Time - The New Birth

It’s a long time since I did it, said the young girl to the lad.
And why is that the young boy said, was it really all that bad?
Well, no, it wasn’t all that bad, she replied with a cheeky grin,
But the one with who I did it, just couldn’t get it in.

Well, that got my ears a twitching, so I moved closer in to hear
What--- it was that she was talking bout, but just as I got near,
He whispered something to her, and she punched him in the snout,
I bet he thought what I had thought, that she was talking bout?

Been listening to the South Park CD in the car.

One of the tracks samples The Immigrant Song.