The stockable variation is first introduced in level 27 and adds 15 seconds to the timer at the start of the level. Once the extra time has elapsed, extra time candies cannot bring the extra time back, reverting to the normal time limit for the rest of the level. This variation is only available on web version.
20 (6.67 each)
55 Save 8% (6.11 each)
90 Save 25% (5.00 each)
It also appears when you fail to reach the target score when time runs out, and will refill your time by 15 seconds. You have to spend gold to use it, and you cannot stock this booster to get this effect. +30s and +60s versions appear if you fail many times consecutively without quitting. This variation also appears on mobile versions.
Many players will never buy this booster and will simply use it wastefully because:
Many timed levels are already so easy, some easy enough to reach three stars, without boosters. This is no longer the case for high timed levels.
Most timed levels that are hard usually have candy bombs. The player will still lose the level if the bomb timers reach zero moves, regardless whether the player uses this booster or not (unless other boosters are used as well). Now, high timed levels are almost always difficult, and are often extremely hard to earn three stars.
In addition, to use the booster, especially when the player is about to fail, usually gives enough time to get only a one-star score.
Most levels have time limits much higher than 15 seconds. 15 seconds is a very short time limit in a Time Level.
Either way the booster is not much use to the player, and it is especially not worth the money.
Do not use the consolation variant (one with the +15 or so) in any case, no matter how close you are!