In one aspect, a method includes identifying an upcoming content modification opportunity on a channel. The method also includes responsive to identifying the upcoming content modification opportunity on the channel, identifying a group of multiple content-presentation devices tuned to the channel. The method also includes for each content-presentation device in the identified group, determining a respective probability of that content-presentation device successfully performing a respective content-modification operation in connection with the identified upcoming content modification opportunity on the channel. The method also includes using at least the determined probabilities as a basis to select, from among the content-presentation devices in the identified group, a subgroup of content-presentation devices. The method also includes performing actions that facilitate causing each of at least some of the content-presentation devices in the selected subgroup to perform a respective content-modification operation in connection with the identified upcoming content modification opportunity on the channel.