some market makers get out completely like you said. but many who work as specialist (not many in OTC markets, mostly an exchange phenomenon)hold a position almost 100% of the time. MM but more specificaly specialists by law have to stand ready to buy or sell and the firm bid and ask to maintain a market, whether it is aligning buyers and sellers or for thier own accts. Obviously the pre and post market portions of that dont apply to pinkies and the like.