For me, I learned shortly after I started writing that the publishing houses couldn’t get back to me for months. So, rather than be a victim to the state of the industry, ever-increasing slush piles, I decided that I would not just send my work to one publisher, but to as many as I thought it suitable. I do inform them that it is a similtanious submission and let them take it from there. So far, I’m happy with the response times. I don’t feel I’m wasting my life waiting for one manuscript to come back so I can send it to someone else.