This is the way that the unlimited lives in the game work. The timer begins when you obtain the unlimited lives and does not stop, even if you close the game or your turn off your device.
Actually, the timer on my unlimited lives always stopped when I turned off my device. Was it not supposed to work that way? That's how I built up to over 30 hours at one point; I was down to 23 when the update wiped them all.
This was a glitch unfortunately. The unlimited lives are designed to work as per my original post, the timer will continue to count down regardless of whether you close the app or not.
