Once per address, at least that's what they claim. And it's not the most recent version, the one I got was about a month old. Still useful to see what it's all about, and recent enough to be fairly accurate, I figure, but if you're looking for latest prices across the board, splurge for their $13.75 pack. (I presume you're already aware, but in case not, the regular weekly edition does not have pricing for everything. It's type coins, mostly)
FWIW, I actually got two editions in my free pack, a regular edition and the not-quite-most-recent monthly.