Libraries rarely report back until there is a deal, or at specific pay periods, quaterly, semi-annually or annually. If you have new material it can give you a good excuse to contact them. You can say, “Are you looking for anything right now?” You may hit them on a good day. As long as your attitude is what can I do for you, rather than give me, contacting your clients can be helpful with any business to business relationships. Connecting on FB or Twitter can help. Some libraries have public and private pages where they can stay in touch with composers regularly for new needs. If you can get to know clients as human beings you may discover there just like you, and have lives, families, etc. Who do you like to work with? Friends, right?. As far as waiting for the money, this is a marathon, not a sprint! It will take years to get things going. It will be a combination of a number of libraries, and clients that will pay off. Never wait for a check. Keep finding new clients. Eventually, you will be busy, and when you least expect it, you will get a nice email telling you your music has been placed, and you will see a check in….wait for it….3 to 6 months!! Patience grasshopper.