One More Minute
When playing games with a time limit set the timer with one minute less than the agreed total. Then when the timer goes announce that the group are into their last minute and restart the clock.
Splitting the time this way can help improve focus. Rather than suddenly running out of time players can be given a chance to make a last ditch effort. Also pausing the clock can give them a few extra seonds to assess a situation and depending upon the activity adjust their strategy. It's even possible to sneak in a bit of drilling or practise for anything troublesome that has cropped up during the game.