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I can't say I totally understand your post @julzie68, but I think I get the gist of it.
Timed boosters from F5 can't be stopped, or saved so once they start running you either use them or lose them. I agree though that it is annoying that you generally seem to win time boosters after you have played for two hours or more, or lost all of your lives.
Unfortunately this is just the way King likes it, so I am sorry that you are unhappy, but there is nothing I can do to help you.
Welcome to the King Community.
I know the reason for your frustration is that you are missing out on the benefits of free boosters because you don't have lives despite having a free booster. However you can add a few active friends to your game and exchange countless lives.
Thank you!