My partner was born in 1970s and grew up in London. I am an immigrant.
He's now in his 40s and fairly professional and still uses a lot of slang language that he grew up with intermittently with friends and colleagues, for example:
Jack diddly squat
Brown bread
Bird (talking of me)
Snuff it
You get me
Bump off
And similar...
He also says 'Valentimes' instead Valentine's although he spells it correctly! 
I don't correct him as English is not my native language but I find it somewhat stuck in 1980s and do think a grown up man would have grown his vocabulary as he was building up his life and career.
But maybe it's more common than I think?