That's apparently how long the traditional music download format of iTunes has left.
Within 24 months, Apple will move away from the old model of digital downloads (newer than the ancient model of physical purchases. Remember CDs? Ha) to throw all its weight behind the fresh new world of its streaming subscription service, Apple Music.
Paul Resnikoff of Digital Music News has been tipped by sources "with close and active business relationships with Apple" that a move to music streaming subscription over and above downloads is a question of "not if, but when". While Apple still makes several hundred million dollars on iTunes downloads each year, that figure has been steadily falling since the heights of 2012.
Apple is currently considering a number of timetables for the switch over - none of which seems to maintain the current music download model indefinitely. Apple might stagger the phasing out of iTunes sales in nations where Apple Music is making increasing profit: while nations like the US and UK could see iTunes downloads shut down in two years to push users toward Apple Music, "tier 2 and tier 3" nations could maintain a download model for longer.
Another option sees Apple maintain download sales for a further three or four years, waiting for Apple Music profits to overtake the doomed iTunes model before they axe it entirely. Once source apparently told Resnikoff that if Steve Jobs were alive today he would have already "killed" the iTunes model.
The man leading the charge to ditch iTunes in favour of Apple Music is apparently Jimmy Iovine - a former Universal Music Group executive and now top Apple Music executive. Iovine would rather de-emphasise iTunes as soon as possible, pushing users toward a subscription model, putting Apple into increased competition with the likes of Spotify.
We'll unlikely learn anything concrete until Apple's annual developers conference in June, an event which is expected to reveal a series of significant Apple Music improvements. Until then, we'll stick to the oddly overlapping beats of iTunes and Music.