My wife's idea of me saving money in the hobby is 'don't buy anything else, ever again, from now until death'. However, that's not going to happen. One thing I have done is limit myself to 20th century topics, which is my favorite era. I also have a lot of Napoleonics plus ancients, medievals, colonials, etc., but if I keep trying to add to those collections in addition to the 20th century stuff I'd go broke, which my wife would really not appreciate since we just bought a house.