Rob,
Were you referring to the Wal Mart Gillette blades like
these, or the 7 O'Clock variants? If it's the former you will definitely notice a difference with almost any other blade, especially Feather.
I've never used vintage DE blades but they do have their fans. I think it's thebigspendur who says the old blades would last for 10 or more shaves. But since many old blades were not coated they would be prone to deterioration unless the owner stored them correctly over the decades. Hopefully some vintage blade users will chime in with a more definitive answer.
BTW - I believe member DeLayne (sp?) is a vintage blade fan, you could try sending him a pm...