DisturbMeLater cydia tweak allows you to dynamically choose how long the Do Not Disturb (now referred to as DND) effect should last.
From the Control Center, perform a long press on the DND toggle. A popup will allow you to select the duration of the DND effect. While the timer is active, you can cancel the timer or readjust the timer by again performing a long press on the DND button.
You can still enable/disable DND manually with a single tap on the DND button as you typically would. If you manually turn off DND while a timer is active, it will remove the timer automatically.
Configure options from Settings.