Not OP but from my experience, the LEGO I had in a bin since I was a kid still fit perfectly with LEGO I'm buying for my kids 30 years later. That's unbelievably impressive to me.
Lego from my youth, which was a hand-me down at the time, doesn't fit well with new lego. So it might be 40 years old, (which seems like a long time until you actually reach that age!)
I think it's more likely do to plastic aging than the original tolerances though.