Nope! Diaphragms are meant to be reusable. In general, a user might need a new one because of certain changes to her body (weight gain/loss, pelvic surgery, for example). You can check out these links for more information:

Feminist Women's Health Center (http://www.fwhc.org/birth-control/diaphram.htm)
Palo Alto Medical Foundation (http://www.pamf.org/teen/sex/birthcontrol/diaphragm.html)
Planned Parenthood (http://www.plannedparenthood.org/birth-control-pregnancy/birth-control/diaphragms-caps-and-shields.htm)

:)