Looks like it is often cycled
https://examine.com/supplements/huperzine-a/
https://nootropicsexpert.com/huperzine-a/
https://www.lifetropics.com/blogs/articles/huperzine-a
https://supplements.selfdecode.com/blog/huperzine-a/
"Cycling of huperzine-A tends to be used since it can remain in the body for quite some time (half-life of 10-14 hours), and although a 'cycle' of huperzine-A tends to last 2-4 weeks followed by a break the optimal cycle length is not yet known."
"One thing to note is; Huperzine-A has a long half-life of 10 – 14 hours. In other words, it does not leave your system nearly as quickly as most other nootropics. So many neurohackers restrict their use of Hup-A to 2 or 3-times per week"
"Huperzine-A does have a long 10 – 14 hr. half-life so you should cycle it. Either take it every 2nd day, or even twice per week. The benefits are long-lasting and will stay with you."
"3. Cycle it on and off for better results - For every month of Huperzine-A use, take 1 week off."