Q. Are there an infinite number of flies on Earth?
A. An infinite number of flies would have an infinite mass. This would breach the Tolman–Oppenheimer–Volkoff limit leading to the collapse of the earth into a Black Hole. This has not happened, hence there are not an infinite number of flies on Earth, despite the obvious evidence to the contrary.
Q. Will my cold persist for ever?
A. If your cold persisted for an infinite time, this implies that for all possible times t there would be a time t + δt at which you would still have the cold (and hence be alive). This contradicts the human mortality axiom. Hence your cold will eventually stop, possibly via your death, despite how it looks to you today.
Q. Will it ever stop raining?
A. This is England - don't be silly.