The game ends when you run out of droplitz. Playing in Zendurance mode will make these achievements much easier to obtain because the level of difficulty does not go up when paths disappear. You just pick your theme and play at the same pace. It's not as easy as the very beginning of Classic mode, but you're not going for these achievements until you're pretty familiar with the game anyway so the speed shouldn't be something new to you. Although your score will surely increase, the key to surviving is keeping your droplitz reservior full. You do this by creating multiple paths that involve splitting the droplitz. Full Houses, by their nature, can easily double your current droplitz stock because more and more droplitz are being dropped the entire time you're creating it, and the more that fall into splits, the more that get collected and add back to your reservior.