There is not a limit set by ndxCards™ on the length of a note. However, it is recommended that you write a note about one thought, idea, fact, piece of information etc. and associate it with specific keywords. This would make finding this information easy.

A very long note is likely to be about many (though related) ideas. Such a note would likely need to be associated with several keywords, some of which may be only pertain to a part of the note. Splitting this into many notes each with appropriate keywords is probably a better way to keep the data. The related notes can be brought together when needed, while they each can stand alone and be useful in other contexts.