I have no idea if this is a bug, but on the Nintendo Switch edition of Minecraft (Version 1.9.0) I threw some lingering potions down. The clouds did not disappear after at least a minute. The clouds had no effects in survival mode, leading me to believe the actual effect was gone, but the clouds remained for no reason. I hope it is just a visual bug, and not intentionally. (I only know about this bug on the Nintendo Switch version though, since the only other Minecraft I have is the Xbox 360 version, where lingering potions don't exist.)