Luma protects your FIRM0/1 by default. So you can safely update from whatever your current firmware is to the latest, without losing A9LH.
It's also believed that it will protect it during future update, but if an update ever happens, just make sure you wait until it's confirmed safe to update.
I have a question about this. During my installation process of downgrading emunand to 2.1 for my o3ds running luma3ds, i haven't gotten an error on native firm installation like i did with reinand while installing a9lh for my n3ds which was supposedly because of the firm blocking. Why didn't i run into the same error on luma3ds?
Rumiko Takahashi got so much fan email about the character that she brought her back in the manga, it was going to be completely different originally (with the alien of the week type).