This is a common question on renshuu, and like most questions, depends on your situation.
There are two ways that a schedule is technically finished:
The schedule introduces all the new terms
This is the one which, for the renshuu-built schedules, will prompt a "This schedule is finished" message. More specifically, it means that all of the terms have been studied at least once.
The mastery level of the schedule is 100%
This happens when the mastery level of all terms in the schedule is 100%. The vast majority of users will not reach this stage (and that's not a bad thing).
Getting a term to 100% mastery will, using the default settings on renshuu, take a couple of years. This is normal, and common with most SRS learning systems (which renshuu uses). In short, the more you get an answer correct for a term, the more time it takes for it to reappear again in your schedule. This span is just a day when you begin, but can expand out to several months when you get closer to 100%.
While reaching 100% feels great, it is probably not ideal for your learning goals. The key to keeping materials in your head is periodic revision, and when you're interacting with a language, you will end up seeing words more and more often in actual usage (movies, books, conversation with friends, etc.), so revision through a tool such as renshuu is no longer needed.
So when should I stop learning a schedule, and what should I do with it after?
Most learners on renshuu will get mastery levels for their materials up to at least 50%. After that, they typically do one of two things. Consider the following example: the learner has just finished studying the "Words for Japanese Basics" schedule alongside its companion "Japanese Basics" grammar schedule.
1. Learner A loves to always learn something new, so they will immediately use renshuu to create the next set of schedules. While they learn the new materials, they will continue to study the Japanese Basics until they hit a mastery percentage that feels good to them (50%, for example).
2. Learner B likes to have a better grasp on the materials, so even after they run out of new terms on the Japanese Basics schedules, they will not jump into any new materials until they hit that 50% (or something else) mastery level.
Once I "finish" a schedule, what should I do with it?
If you are no longer studying a schedule, feel free to remove it using the Adjust your Schedules link. Removing them does NOT erase your mastery data, so if you ever wish to remake the schedules, they will be just as you left them.
Alternately, what some people will do is rename the schedule to something like "Word review", and adjust the study vectors (Tap the settings icon next to the study button, then go to Currently Studying) so they are studying it much less. Less study vectors = less review. After all, you typically want to spend less time on older reviews. Then, as they get to each new level, then can Merge any older schedules into these larger review packs.
In the end, though, there is no perfect answer for when should stop studying - so do what feels best to you, and that doesn't overload you too much in terms of time!
