Da o per?
So it is: Siamo insieme da trent'anni.
But also: Leggo per trenta minuti.
I don't understand why 'per trent'anni' is not correct. And vice versa.
Is this just one of those things one should just memorize? Or is there some rule to this?
Can somebody help?
Duration forms are one topic in which Italian and English grammar differ quite considerably. The page posted by Maxim should clear Arnold's doubt, but I'll include duration forms in my list of future articles.