Couple nights ago I decided to completely empty the box I had of already prepped cases (.223).
Does "already prepped" mean sized, trimmed and primed? If so you are only talking about 4 batches of 50 and that is pretty typical for me.
All the brass gets cleaned soon after I get home from the range. Later on, I'll size and trim a bunch and leave them in a closed bucket or coffee can. They'll sit like that until I get the time and hankering to prime them. When I'm ready to put loads together I have primed cases waiting. Then it's just a matter of dropping powder and seating bullets.