Rolo has been using his Geass since he was very young and using it beyond limits; for various missions and assasinations again and again. But he never lost control over the Geass like Lelouch and Mao. Also if he had lost control before dying then what would be his situation if he had used it infinitely? Would he stop the time around him forever?
Forever would have been impossible. The weakness to Rolo's time stopping Geass is that it also stops his heart, so he'd die quickly enough from it being in permanent use, which in turn would stop the geass. Same goes for him overusing it. The limit of his geass comes from a sort of body-based time limit (surviving while his heart is stopped) preventing extended use, rather than a limit of the power itself. Below is a quote from this page, which I've spoilered out for plot reasons.
Its weakness was that it stopped Rolo's heart when used, limiting its activation to short bursts. A large number of people was also more difficult to stop, as Rolo was exhausted after he projected a field encompassing a majority of the school's campus. Finally, this Geass was unable to stop inanimate objects or physical phenomena such as speed and momentum. Rolo ultimately died when he overused his power in a short amount of time.
He cannot stop time forever, mainly because of his heart stops every time he uses it. It takes 4 mins of heart stoppage to kill your brain cells. So the maximum he can stop time is for 4 mins (if he has a tremendous will power) after which he will be dead no matter what. Weaknesses of Rolo's geass as descibred in Wikipedia:
The weakness of Rolo's Geass is that his heart stops when he uses it, limiting its activation to short bursts. The range also determines the amount of strain it puts on him. Finally, it is unable to stop inanimate objects or physical phenomena such as speed and momentum (for example, it cannot stop a clock nor a projectile in mid-flight). Although the Geass can work on Jeremiah Gottwald, Jeremiah's Geass Canceler automatically activates when that happens: limiting the Geass' effect on him to just a few seconds.
As you can see from Wikipedia, he has a bunch of weaknesses. Essentially, everytime he uses it he gets a heart attack, even for a second. We all know what repeated heart attacks can do: they kills some of your heart cardiac walls. It not even a temperory weakness. He essentially trades a part of his lifespan every time he uses it. His geass also cannot stop any inanimate object (unlike Sakura's time card :D).
Hope this helps :D
When he uses his power his heart stops beating! In other words if he uses his Geass for a long time he dies because his blood stops circulating!