Yep on what Leftie said. It's in your warranty booklet. From my '13 warranty booklet.
MAINTENANCE , DATA ACCESS, AND
As a condition of this warranty, you are responsible for
properly using, maintaining and caring for your vehicle
as outlined in your OWNER’S MANUAL and your
NISSAN LEAF SERVICE & MAINTENANCE GUIDE,
and maintaining copies of all maintenance records &
receipts for review by Nissan. You are required to perform
annual EV Battery Usage Report at intervals of
12 months, 24 months, 36 months, 48 months,
60 months, 72 months, and 84 months. These EV
Battery Usage Reports can be performed by a Nissan
LEAF certified dealer or any qualified repair shop facility.
The 12 and 24 month EV Battery Usage Report will be
performed at no charge to the customer, provided the
work is done at a Nissan LEAF certified dealer. Any
damage or failure resulting from a failure to have these
required services performed, or that could have been
avoided had these services been performed, is not
covered under warranty...
And, Nissan does change their minds on various things w/no notice/warning (e.g. assisting folks (or not) w/batteries that are down to 8 bars or less after their capacity warranty expired).
I consider it cheap enough insurance to have it done. IIRC, I was charged $39 for the most recent check. I won't bother after 84 months.