My answer has a caveat which is that I am a completist but I do still wait for reviews and overview videos because if the pack is game-breaking (MWS) I do wait until the bugs are fixed. So far, none of the packs with bonus items have been broken enough that I've felt I have to wait beyond the holding period.
I waited about two months before buying MWS (just for the world) and three months before buying Eco Lifestyle (now I see this as an essential pack), but other than that I buy things within a few weeks of release, once I have "clearance"
