The ideas is deliberate practice of each sentence, so learner retain it by practicing and repetition.

Before running out of $1/day limit, a learner would potentially run out of cognitive load to absorb new language material (vocabulary + grammar). Of course there's higher plan with higher limit to keep going.

But if a learner is getting fluent, there's option to use Subtitle mode (no pause), which can go longer than Listening or Speaking sessions, these two sessions are designed to pause (automatically or manually) after each sentence to breakdown vocabulary and grammar.