I managed to get to the last upgrade of level 4 in blacksmith in the end of act I by using the party money to upgrade only one character. From now, I need these blacksmith pages to upgrade, and they can only be obtained in Nightmare mode (or on act IV, whatever).
I craft items that are already useful or will soon be useful, i.e., level requirement on items is not my worry now.
The bad thing is that now it's gonna be a little hassle to get those pages before Nightmare, so I want to know, is it viable to upgrade? More specifically: do all items made in level 5 require high level (~ 35+), or more important, do they take more stuff to prepare that I do not have access now, on act II?