Save "extra time" boosters

There should be a way to save the boosters we get as prizes or rewards that are good for extra time ( good for 30 minutes, or two hours, or whatever) so we could use them later. As soon as we accept them, the time starts and very often I get these at the end of my play and have no lives left to use them. Or they are boosters that I can't use in the level I am currently playing. So these great boosters that we earn become useless. What kind of reward is that if you can't use it? No reward at all! Making these boosters able to be saved for later use would be a great addition. When we collect the prize, instead of a single "collect" button, how about having two buttons: one that says "use now" and another that says " save for later". So many of my extra time boosters are wasted.