Iridium satellites are being replaced, once SpaceX resumes flights.
QuoteOne thing the new satellites will not be capable of doing, however, is producing Iridium "flares". These are the flashes in the sky that result when sunlight glints off the antennas of the old spacecraft.
The new satellites do not have the same configuration, so once the original constellation is de-orbited the flashes will cease.
http://www.bbc.co.uk/news/science-environment-38613275
Yep, we have 1-2 years at most before they are replaced with a new set of satellites. The new ones will not flare like the existing Iridium constellation.
So, get out and enjoy the Iridium Flares whilst you can as their days are numbered.
:(