The QD is the part that connects the end of the headset cord to the long curly cord that goes into the phone. Headset respect begins with the QD. Pulling on the wire or on the cord™s strain relief instead of the QD is a common cause of failure.
Eventually the wires will break causing intermittent static or lack of transmit or receive sound, or all three. (As a side note, if you quick disconnect during a call, your caller will be put on silent hold until you reconnect.) If handled correctly, a headset can last for years.
If you need more cord length, consider adding a ten foot extension cord, PL-40703-01, or consider switching to a wireless headset.