Interminable

[Sarah]

Without termination; admitting no limit; boundless; endless;wearisomely protracted; as, interminable space or duration;interminable sufferings.That wild interminable waste of waves. Grainger.

[Sarah]

Without end. Unending

[Dave Paprocki]

continuing for too long and therefore boring or annoying:

[Lanell]

Endless (often used hyperbolically)