When you receive time for unlimited lives in the game, once you claim this time, it will continue to countdown even when you're not playing the game.

For example, if you got 6 hours of unlimited lives and played for 1 hour but did not play again for 3 hours, you would have 2 hours of unlimited lives remaining, and not 5.

Please note that this also applies to the time breakers (boosters), as well.