It depends on your business industry, type of callers and marketing plan. Assuming that you take a profit driven approach to using your telephone on hold messages as a marketing tool, you will want to consider changing at a minimum of twice per year, however its best to be more proactive and update more often like quarterly or even monthly. Callers love something new and refreshing (don’t we all!), particularly those that frequently call back and are placed on hold! Why not inform them them of special promotions, new products, or customer service info – there’s always something more that can be said! Make the most of your telephone’s on hold messaging infrastructure. It is an effective way to win, retain, and sell your callers on hold.
You will most likely run into the typical Stalingrad-esque repeating messages that state how important your call is to the business. It is only slightly less annoying to have some form of default music that plays on a loop, and gives you the virtual experience of being stuck in an elevator, listening to muzak ad infinitum.

Your Message on Hold content should be updated in conjunction with changing information at your company. These changes might include marketing efforts, customer service strategies, policies, promotions, or other news.
The primary feature of on hold messages is that they provide a way to keep customers informed about your business. Instead of silence or elevator music, businesses can use their hold time to provide hours of operation and other useful information to their callers. Additionally, the wait time may be used to promote new products for demand generation. This can be a great tool in up-selling and cross-selling items to consumers while they wait.