It all depends on how interested you are in the stuff they're packing, obviously.
For instance, if you watched a bunch of unboxing videos and think, "I like 80 - 90% of the stuff in there" then you can probably go ahead without regrets and just periodically offload the stuff you don't care for on friends or whatever. Once you get to a level of like, "I'd only like about half the stuff in these boxes", then it's not worth it.
TL;DR the question you should be asking yourself is: "Am I better off paying separate shipping on stuff I know I'll like?"