Re: How many expansions and boosters are too many to use at once?
 

I know there are certain cards that can cause game-breaking problems if anybody were to get a hold of two copies at once, but I can't recall if any of them are in the base set.

Re: How many expansions and boosters are too many to use at once?
 

I've never felt deck dilution was a problem. But the Listen at the Door rules seem to help cycle through cards quicker, potentially helping you get to the combos you like. That being said, throw in as many expansions as you like. But keep in mind more expansions equals more rules to keep track of. Steeds, hirelings, dungeons etc. So for beginners it might be best to ease them into the additional rules.