There is a specific cutoff in furniture and cars...a certain number of years old and you can say antique, regardless of any other attribute.
What makes vintage in clothes? The dress in my other thread is 30 year old Talbots. And not kidding, I think better quality than today....not just considering Talbots, but most stores. Better material by a long shot, but I also think better construction. Based on the shopping I've been doing lately, a dress of this quality and material would be above $300. But is it vintage... or just old?
Is vintage determined by a strict number of years, or by years plus a quality rating (as in, a 30 year old ON dress might not make the category), or is it even more nebulous, adding some component of judgment about whether the style is currently desirable?