Revelation 9: 5: And to them it was given that they should not kill them, but that they should be tormented five months: and their torment was as the torment of a scorpion, when he striketh a man.
The demons loosed from the Bottomless Pit under the fifth trumpet were likened to desert locusts whose lifespan is five months. These devils have been loosed to torment those who rejected the Word. And as a desert locust dies after five months, so will these tormenting devils be eventually destroyed in the Lake of Fire.
The fifth trumpet was also the first woe (Revelation 9: 12) or World War One. The five months here also represent the five years of war that ravaged the world, from 1914 to 1918.