Monthly plans for all courses and curricula. Unlimited = read all*; Unlimited+ = read and practice all*. Certification stays per course.
Reuse works best when content is modular: keep lessons small, separate explanations from assessments, and use shared question banks where possible.
Reuse becomes easy when your content is modular and consistently named.
Copy-paste creates maintenance pain. Prefer linking/shared resources so updates improve multiple courses.