Specialize or not?

Market conditions change all the time.
If you are running a business, it's a very good idea to keep in contact with multiple buyers, and try to go after the stuff that can get the most $ per hour of labor ( after expenses ).
Also a good idea to educate yourself on electronics collectibles ( IE: many old slot cards from before 1990, vintage electronics testers, e.t.c. ), rare/desirable components ( example: white ceramic ICs ), precious metals, exotic metals ( tantalum, ruthenium, indium, germanium, e.t.c. ) , and parts that sell well (vintage knobs, metal gears, working vacuum tubes, e.t.c. ) .