A method for content delivery includes selecting one or more time intervals. During each time interval among the selected time intervals, given content is prefetched from a content source to a communication terminal using a guaranteed prefetching mode, by continuously tracking the given content on the content source, so as to detect changes to the given content as they occur during the selected time interval, and maintaining the communication terminal continuously synchronized with the content source with respect to the given content, throughout the selected time interval, notwithstanding the changes that occur during the selected time interval, by continuously prefetching at least part of the given content from the content source to the communication terminal. Outside of the one or more selected time intervals, the given content is prefetched using a best-effort prefetching mode, by tracking the given content less frequently than the guaranteed prefetching mode.