Feature summary:
Document on API help pages like https://en.wikipedia.org/w/api.php?action=help&modules=edit and/or https://en.wikipedia.org/w/api.php?action=help&modules=main#main/datatype/expiry that "6 months" is the maximum expiry for watching stuff.
I'm not sure why that limit even exists. I was offering expiry times up to 2 years in my script, not knowing that anything over 6 months would throw an API warning which is how I found out the limit exists at all. Btw, 1 or 2 years is not unreasonable, some discussions can run for a long time but that doesn't mean permanent watching is warranted. But whatever, if there must be a limit at least document it.
Instead of updating the documentation, removing the limit would also be a good solution if that's possible.
Use case(s):
I read those pages. I follow what they say. They didn't mention a limit, so I assumed there was none.
Benefits:
Save me from embarrassing errors.