In my opinion you should. If you update it now, even if you're not going to use it, you won't FORGET to update it (I'm great at forgetting stuff myself haha).
I'm fairly new at computers myself, so take it with a grain of salt.
The purpose of dual bios is the ability to easily reset settings if something goes wrong in an overclock.
If you "abuse" your primary bios and it "breaks" you're able to boot up with the secondary one and "revert the primary".
I own a 1070 FTW myself and it's both my first premium card and first dual bios card.
At least for this card, I think, the Slave bios enables higher OC potential - If I recall correct the slave bios can use a higher power target, or something or other..
Yeah if it isn't obvious, I'm not overclocking yet (or experienced with it) - BUT SOON!

Edit:
Or just listen to Jacob, and don't update it at all :p
You will be fine, not having it updated :) Especially if you're not going to use it.
Aenmond
Hi. Noob questions: I have a 1080 FTW. If I don't plan to use the Secondary BIOS, should I update it anyway? What are the advantages of the Secondary BIOS?